The short answer is:
- If she was less than three years old at the time, she can marry a Cohen no matter who the molester was or what age he was.
- If the molester was less than nine years old, she can marry a Cohen no matter who the molester was or what age she was.
- If there was neither vaginal nor anal intercourse, but only other types of contact such as oral sex or fondling, she can marry a Cohen no matter who the molester was or what age they were. (However, even partial insertion of the penis is considered sexual intercourse.
- If the molester was a Jew whom she is allowed to marry (see below for details) she can marry a Cohen no matter what age they were.
- If there was intercourse, and she was three years old or older and he was nine years old or older and it was someone whom she is not allowed to marry (such as a non-Jew or a close relative (see below)), she may not marry a Cohen.
- If she was married, and the molester was nine years old or older she may not marry a Cohen whether it was rape, mistake or voluntary.
- In any case where there is doubt as to who the perpetrator was or whether or not there was sexual intercourse, an expert Rabbi must be consulted.
The long answer:
A Cohen is forbidden to marry a divorcee, a chalalah or a zonah (see Rambam Issurei Biah 17:1).
A divorcee includes one who was divorced after erusin (Rambam Issurei Biah 17:18) even though she didn't yet have nissuin, even if she is still a virgin. Erusin is the first part of the wedding ceremony where the groom gives his bride the ring and declares "harei at m'kudeshet li etc." Nissuin is the second part, which is either the reading of the sheva b'rachot under the chuppah or the entering into a private room afterwards.
There are three kinds of chalalah.
- A woman whose mother was a chalalah is a chalalah.
- A woman whose father was a Cohen and whose mother was forbidden to a Cohen is a chalalah (This case actually falls under the first case. Since the cohen was forbidden to be with this woman, he made her into a chalalah. Therefore she is the daughter of a chalalah).
- A woman who was forbidden to marry a Cohen who had sexual intercourse (Whether vaginal or anal intercourse, but does not include oral or manual sex. See Rambam Issurei Biah 19:2) with a Cohen becomes a chalalah.
A zonah includes several categories, but note that it does not include the most common translation of the word which is prostitute. A non-married Jewish girl who sells herself for sex or freely has sex with everyone, as long as she does not have sex with someone whom she is forbidden to marry such as a non-Jew or a close relative is not a zonah and may subsequently marry a Cohen. In regard to a Cohen, the word zonah is a technical term and someone may become a zonah in regard to these laws through no fault of her own, and no one intends to insult her thereby.
The following are considered zonah for the purposes of the prohibition to marry a Cohen:
- A non-Jew
- A convert
- A Canaanite slave
- A freed Canaanite slave
- A woman who had sexual intercourse with a man with whom she was forbidden to have sexual intercourse (Whether vaginal or anal intercourse, but does not include oral or manual sex) based on a general prohibition (As opposed to a prohibition limited to certain classes of people such as Cohanim). This includes close relatives, non-Jews, mamzers (The halachic term mamzer is not the same as the English word bastard. A bastard is one whose parents were not married to each other. A mamzer is one conceived from a union which was forbidden and was punishable by caret (excluding the case of the mother being a niddah)), Canaanite slaves and for a married woman, any man other than her husband.
- It does not matter whether she knew that it was forbidden to be with the person or not, and it does not matter if it was voluntary or forced or by mistake (Rambam Issurei Biah 18:6). Therefore if (r"l) a Cohen's wife was raped, he is required to divorce her.
For purposes of these laws, close relatives include:
- father or grandfather
- son or grandson
- step-father or step-grandfather
- step-son or step grandson
- father-in-law (even after she is widowed from her husband)
- adopted relatives are not considered relatives for these laws
Neither uncles nor cousins are considered close relatives for this purpose, and in fact a woman is allowed to marry her uncle or her first cousin.
In all of the cases of zonah and chalalah, the woman becomes forbidden to a Cohen through an act of sexual intercourse. This includes either vaginal or anal intercourse. It does not require full penetration of the penis. If the entire head of the penis entered either the vagina or the anus, this is considered sexual intercourse for all of the laws of the Torah. If only part of the head entered or it is in doubt, an expert rabbi should be consulted.
Throughout the Torah, and specifically for these laws, for the act of sexual intercourse to have consequence, the female must be at least three years old and the male must be at least nine years old. Therefore, any molestation of a girl under three years of age has no effect on her status, and she is considered to be a virgin. Similarly if the molester was below the age of nine, the intercourse does not count and she is considered a virgin.
So too, lesbian sex and bestiality, even though they are forbidden, are not considered sexual intercourse to affect someone's ability to marry a Cohen.
Sexual acts other than sexual intercourse, such as oral sex (both fellatio and cunnilingus), fondling or other types of manual sex, masturbation, kissing, etc. do not affect a woman's ability to marry a Cohen.
On the other hand, if there were sexual intercourse of the type that would forbid a woman to marry a Cohen, it does not matter if it were voluntary or by rape or by mistake.
In any case where there is doubt as to who the perpetrator was or whether or not there was sexual intercourse, an expert Rabbi must be consulted.
A regular Cohen (as opposed to the Cohen Gadol) may marry a woman who is not a virgin. So if a woman (or girl) had sexual intercourse with a Jew (even if she was above the age of three and even if he were above the age of nine) whom she is allowed to marry, even if they were not married, she is still allowed to marry a Cohen after that. It does not matter is it was voluntary or rape or error.
These laws are given by Hashem in the Torah. They are not designed as punishments or insults. They are a recognition of the special holiness of a Cohen. The laws are based on his status as a Cohen, whether or not he receives the privileges of a Cohen and whether or not he performs the duties of a Cohen. If a woman who is forbidden to marry a Cohen marries a Cohen (or has intercourse with a Cohen not in marriage) she commits an aveirah (sin). In addition, her children are chalalim. This means that even though the father is a Cohen, the children are not. In addition, the status of chalalah is carried down in the female line, so that her daughters, their daughters, etc. may never marry Cohanim, and if they do, their children will not be Cohanim.