For sure. Considering the situation and her fiery temper, Abby will very probably go in with all guns blazing as soon as she knows/suspects strongly enough, and there won't be anything that Frank (or Lilly) will be able to do to deny her at that point. Frank will probably try, of course, but it'll be a lost cause--he's on super shaky ground because of his affair with Lilly, and I guess he knows it. His only hope at that point is probably that Abby never realizes what is going on, because as soon as she does, he's screwed.I think it will come down to that. After all, you can call it backstabbing when you consider who Frank is involved with: Not just Lilly, but also Becca, and Meiko. Casually, there's also Madison and the judge's daughter. If we ignore CNG's revision and assume that Lilly and Abby are dating, then Abby can still argue that at worst Lilly is cheating on her, at best she's still hiding her relationship with Frank, which runs parallel to the Abby-Lilly thing.
And even with the retcon on CNG's part, you can still argue a massive abuse of trust against Abby: Lilly more or less knows that Abby wants something from Frank (quote Lilith: “I don't trust her with you”) and Frank also knows about Abby's feelings. Enough reason for Abby to pull out the big guns and issue an ultimatum.
Figuratively first, and then quite literally, ofc.