I'm not entirely sure where you're going with it, but I'm willing to wait to find out.
So, this Jess character, Frank's ex, has decided to force him to leave the band - apparently to ruin his life as he ruined hers by dumping her? Then, after he leaves, she auditions for the band, knowing that she can replace him, likely making the torment on poor Frankie much worse.
What I'm slightly confused about is why Frankie believed her threat about killing the band members - it's a little hard to believe that a simple threat would be enough to force him to drop the band. Why didn't he go to the guys or Brian? Security? Police?
Update soon! I can't wait to find out what's really going on.