As for why did that with her "friend", we wouldn't know. Niggas on here would tell you she a hoe, but ስንት fucked up የሆኑ ሰዎች are the way they are because of a psychological disorder that we ignore😒. And she did this before she met you man. Breaking up over that is like denying የለቅሶ ቤት ንፍሮ because ሌላ ሰው ስለዘገነው። የዘገነው ሰው ኮሮና ከያዘው ላሽ ትላለህ፣ ካልሆነ ዘግነህ ትበላለህ። It all depends on you though. If you don't like her entanglement then you don't like it and you say bye to that girl. But you came here. Which means you care to an extent. If she says it's stress, then ask, "What does you stress over to do that?" If it was sth huge like her parents abused her ምናምን, it's understandable. If it was bc የሞላችው card ቶሎ ስላለቀባት, then run away from that bitch. Conversation man. Communication. These should come first before any action. So before you forgive or you don't, you should understand why she did it. Then you decide. And you'll finally be satisfied with that decision. Good luck mate. Cheers✌️🏾