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It is not uncommon for a friendship to progress to something more. She must have some attraction to you if there had been intimate contact of any sort.
Even though she has a boyfriend at home, it is possible that the distance from him and the closer proximity and relationship with you is causing doubts for her in regard to that relationship. You may want to have her define what does she want because although she's said she wants to remain friends, she's giving you mixed messages. At least she should either break up with her boyfriend or halt leading you on.
The best thing at the moment may be to see how she continues to behave towards you. She already knows how you feel about her (or has an idea) At this point, you would want her to make her own mid. The two of you may discuss like you did the pros and cons of dating a friend. Even partners within a relationship are also friends to one another. Neither being platonic friends not being romantically involved are situations that at one point or another cannot change. Even friends have feuds and can end their relationships. She may seem reluctant to rush into a relationship until she handles her affairs with her boyfriend, address possible guilt, etc on her part. Nothing is deterministic and it is possible that with time she can become more aware of what she wants and let you know. Meanwhile, you can still be friends with her and let her know that the only intimate contact you'd engage in with her is only if you're sure she wants to be more than friends.