Relationship advice?

so I have this friend of mine she has a boyfriend but we both got close and we started dating each other things went where going well... we hooked up at couple of times... went out on trips.. it was fun but now out of the blue this women wants to stop this relationship because she finds it guilty to be hooking up with both of us (her boyfriend and me) so she wants me to just be her friends with her and nothing more
what do I do about this
I loved her a lot and I honestly thought she would breakup with her boyfriend in the long run
Relationship advice?
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