Maintaining a good friendship

We have been best friends forever. OK, maybe a bit more than that. But it's hard to stay just friends when she is incredibly hot, shares very liberal views about sex and likes boys and girls. Through the years, we have managed to parallelly enjoy our friendship and very passionate sex. We always knew when was the right moment, and we would just let our urges drive us, and enjoy in hours and sometimes even days of a serious fuck fest.

When she started a serious relationship with her new boyfriend I thought that our sexual relation has come to an end but we continued to hang out as just friends. However, after a year she started telling me that she and her boyfriend are experimenting with threesomes, but so far they have only included other girls. She also wanted to try it with with two guys, but she wasn't sure how her boyfriend would react. From the way she was talking, I understood that she wants me too be the second guy, but I was also reluctant. A month later, I was hanging out with my friend and her boyfriend at her house and we all got relaxed and a bit drunk. At one point she went to the kitchen. When she came back, she was wearing only a micro bikini. "Hey boys, how do you like it?" she asked. I was speechless but her boyfriend just laughed and said that they talked about it and that he is ready to do whatever makes his girl happy. That was a big relief for me, since I missed fucking her a lot, specially after seeing her in that outfit. We approached her started to kiss her all over her body, She got on her knees, gave us a blowjob and we fucked her hard, in all of her holes, for the rest of the night. I could tell she really enjoyed which made me happy too. We stayed friends and a bit more than that until today.