Unmarried women do not have to go to the mikveh... The mikveh is used to purify a woman who is married and has marital relations... But here is an article which discusses this topic:
http://www.yoatzot.org/question.php?id=3089Mikveh for spiritual purification
Although I was born jewish, I didn´t know that. I have been in churches and others places of catholic people because all my classmates were of that religion, but now that I am doing tshuva I want to know if I have to go to a mikve because I feel as if I had a lot of tumah inside me because of that...I am 20 and I am single..
Thanks..Dear questioner,Thank you for your question.
If you are sure of your Jewish roots, but were unaware of them until now, all these years you were considered akin to a tinok shenishba (a babe who was taken into captivity, referring to your spiritual world). It is wonderful that you are reclaiming your heritage and it is best to look to the future. Focus on study and beginning to practice the laws and traditions, rather than look back. You are not held entirely responsible for not acting like a Jew if you did not know you were one.
Jewish law today does not encourage a single woman to immerse in a mikveh until just before her wedding. Traditionally, prayer and tzedakah (giving to the poor or doing good deeds) are considered no less purifying to body and soul then immersion in a mikveh.
However, there are places which permit unmarried women to go to the mikvah for purification and teshuvah (repentance) purposes the afternoon before Rosh Hashana and/or Yom Kippur. At that time, you could check your local facilities.
We wish you much hatzlachah (success) in discovering the beauty of Jewish life.
http://www.yoatzot.org/question.php?id=8979 Mikveh for renewal after treatmentI appreciate your consideration of this question. Is it Halachically acceptable to immerse in the mikveh for the purpose of spiritual renewal and cleansing after undergoing chemo & radiation?
thank you.Dear questioner,Thank you for your question.
In addition to when she is becoming tehorah, a married woman is permitted to immerse in a mikveh whenever she is tehorah already. Therefore, she may immerse specifically for spiritual purposes as part of recovery from chemotherapy and radiation, so long as she is not niddah when immersing.
Single women do not generally immerse in the mikveh, even for spiritual purposes. A single woman wishing to immerse in this situation would need to ask a specific halachic question.
http://www.yoatzot.org/question.php?id=3024Single woman: immersion for teshuvahI am unmarried and haven't been to a mikveh. However, for other personal spiritual reasons, I would like to immerse. The reasons have nothing to do with relations, rather, to set right something I feel was wrong from many years ago. May I go to the mikveh at any time or should I follow the laws of Nidah and count the 7 white days?Shalom,
Dear questioner,Thank you for your question.
A single woman is discouraged from immersing. However, should you wish to immerse for purposes of spiritual purification and repentance, there is room to do so; most women's mikvaot only accommodate this on Erev Rosh HaShanah and/or Erev Yom Kippur, if at all.
Since the immersion is not for purposes of family purity, you need not and should not follow the laws of niddah beforehand.
Other, traditional means to perform teshuvah are: to pray, to give tzedakah, to perform chesed, and even to fast. You may wish to contact a local rabbi for guidance.