Hey there!
Okay, so, with only a few more days, it could be a little tricky.
Have you already met, captured, and transformed Xavier? Once you've done that, Petra will be next. After you reach the end of her path (which you have) a few in game days later she'll be coming to you with a problem you can help. So this clock may already be started, and I hope finishes just in time!
Otherwise, the gem people most often miss is Mason's. You might not have time to start him and reach the end, but to start if, you'll want to talk to Mason once you reach chapter 2 and he'll open up about his past. Once that's does, visit R&D every day and you'll eventually trigger the start of his path.
I hope this helps!