At any age men and women ask themselves questions about sexuality and why things happen. It gets complicated especially when hormones are involved! Answers usually are all we ever ask for in life but when it comes to sex and sexuality there is a whole gambit of varieties of who’s and why’s.
Whether your friend is a lesbian or not is not necessarily an issue. Why you two fooled around may not be an issue either. Life happens in many ways and questions and confusion will arise. But if you can be true to yourself every moment, there should be no shame, guilt etc… about who you are. You aren’t perfect and neither is she. You are constantly changing and so is she. At risk of sounding cliche, Life is a journey, not a destination. For you it is only the beginning, so take it in stride. Life is too short. I am not encouraging either of you to pursue the cheating in any way but to take responsability in the consequences of your actions. Dynamics between you and her may change, her and her girlfriend also. Be patient when it comes to acting out on love or what you think may be love may not be. There are as many varieties of love as there are sexualities. They go hand in hand. But start by getting to know who and what you want now and the rest ought to fall into place.
Best of luck to both of you.
M. for Alterheros