Angry af

Hi guys, So I have liked my best friend over a year but many of the times when I used to compliment her genuinely or flirt with her she sometimes gave a happy reaction and sometimes totally bad because her bf saw my conversations and she used to guilt trip me saying you make me feel attacked or I have bent so many things for you and all and made allegations like you are THARKI and want to get close because I want sex from her and I have to explain all my emotional attachments to her again

Now I found out that she has been having casual sex with a dude from her internship. She told this to a mutual friend but I just don’t get it that if you are in love with your long distance boyfriend and plan to marry him in future then why have sex with other guys? Does lust trump love and is it normal these days? I am also so pissed that she has been guilt tripping me and yet does the same things she accuses me off!