Could a Jewish teenager go to the mikvah if she is not married and has been raped? If a girl has been raped is it acceptable for her to go the mikvah in order to cleanse herself or is this not acceptable or allowed?
See this similar answer from yoatzot.org. While certainly someone is looking for an experience to mark a change from the past, we generally frown upon having single women use the mikvah, though there are different customs about the day before Rosh Hashanah or Yom Kippur. So if your community lets women go to the mikvah then (many Lubavitch communities have this practice) and you feel it would help you, then fine; otherwise, it's really best to find some other thing to focus on towards your recovery.
If you'll pardon my editorializing, I spoke with a psychologist whose primary work is with severe religious guilt. He said he's seen too many instances where "I need a mikvah to atone for my guilt" has led to obsessive-compulsive behavior. (I realize what you're discussing isn't guilt, G-d forbid!, but a need for a break with the past, but it illustrates the concern of when we try to turn mikvah into something it's not.)
I think that this would be a good question to ask a Rabbi. See the many different reasons why this is important, especially when it comes to situations outside of the norm.
However, it would be understandable for a person to want to keep this kind of thing private, even from a Rabbi that they have "made for themselves" and are close to, (Avos 1:6). I have had questions for Rabbis that have made me uncomfortable, though they came nowhere near being this personal. What I do for these questions is state them generally and in the third person. So here, one could ask,
"Can any exceptions be made for the general disallowing of an unmarried women's using the mikveh, like for example if she was raped and would like to use the mikveh to represent a 'new start' as part of her recovery process?"
No introduction or spilling of guts or unwanted pity, just question and answer and done.
Another measure that could be taken is to have someone who is already close to the person and knows about this event ask the Rabbi, in the same way as above. The purpose of this would be to add another layer of interference to make the person more comfortable, like if the person was worried that their body language would give themselves away.
I don't know how relevant this source would be, but I think it adds to Shalom's eloquent remarks about "the concern of when we try to turn mikvah into something it's not". Shabbos 14a discusses a Rabbinic decree that drawn water causes impurity because people started to think that the bathing they did after immersion in caves where the water was unpleasant was part of the purity process.
So the Rabbis made you go to the mikveh again if you bathed after the first immersion, just so you would be clear about what exactly makes you pure. They clearly felt that it was important for this process not to be misconstrued. I'm not saying that no exception whatsoever could be made, particularly in a one-time case where it could aid in a person's process of psychological healing. But I thought it was worth mentioning, again because rape is not something that requires ritual immersion for any halachic reason.
There's no halachic reason to go to the Mikva after rape unless it renders the woman nidda after she's already been married this would apply only if she is a besulah or has only had relations few enough times that relation that they still render her nidda