Now this would be a good deal more interesting. Jackie actually tells Marco that she's coming with on his attempt to find Star again, probably with Janna, Tom, Ponyhead, and a few other tagging along (like Spider and Eagle join "Team Marco" to try and get Ludo back). I could imagine Toffee using proxies against them on their journey (either directly influenced or subtly pushed in their direction) to bring up some doubts in the group's minds on why they're going through with this. Like you said, divide and conquer as they start jumping through various dimensions.
Jackie would try to deal with doubts about this that only get made worse with Toffee's attempts to break the group apart ("Is Marco really just going after her just to help her?" and "Did I come along to help my friend too, or am I only doing this to keep my boyfriend?").
Toffee could play this up against Marco too, making him doubt why he's really doing this, and doubt Jackie for why she's coming along ("Is she here to support me? Or is she just jealous of Star?").
You could get some interesting drama and conflict without shifts to the characters, while also helping to reinforce just how cunning and dangerous Toffee is. He could tear friends and relationships apart without even lifting a finger.