Most Helpful Guy
Generally, you don't date the friend of your ex, that's kind of a bro and girl code thing, so, yeah, you could be mad buttttt is it really worth it? I mean, there are much bigger things to be mad about than who is going out with who
Most Helpful Girl
No, It's not wrong for you to feel that way at all.
Your best friend (especially) should consider your feelings about this.
She should have cared enough to come to you face to face and tell you how she feels instead of "accidentally" doing these things behind your back.
Your friend doesn't sound much like one.
She sounds selfish and only considerate of her own feelings.
If someone is my best friend I see them as a sister.
I would put their feelings has a priority.
I would tell them how I feel about their ex. and see how they felt about things. That would tell me whether I should move forward with their ex. or not.
If they felt strongly against it... well there will be many guys in my life (I find attractive or take interest in).
I wouldn't allow that to break up such a great friendship.
Boys are like buses, they come and go.