I may have missed the issue in which it has been made clear she wasn't jackpot...
Perhaps it hasn't been made 100% clear but having seen Ehret and MJ standing next to each other with Ehret claiming to be a huge fan of MJ's, suggests to me that she is Jackpot.
I suspect there's some sort of weird multiple personality disorder going on here. Jackpot tells Spider-Man that her name is "Sarah Ehret" but when Spidey tracks her down, Ehret denies it and tells him that he should "really keep out of this".
The Jackpot is MJ idea is far too obvious.