I've asked for extra sessions multiple times with my current T, and he was pretty much always able to accommodate me. I found there was a pattern, where I'd ask for an extra session, then when I got there, I'd be thinking to myself "I didn't really need this, what am I doing?" (And would tell him that.) But then, with one exception, they always turned out to be useful, and I was glad I'd gone. (The exception was early on in seeing T, and for whatever reason, in that extra session, he just talked almost the entire time, and I didn't get to share much of what I wanted to. I told him about it after, and that hasn't happened since, in a regular or extra session.)

So I would ask for one. Just keep in mind, depending on how her scheduling is, it's possible she wouldn't have an opening (in which case you could ask her to call if she has a cancellation). And if that's the case, it isn't anything personal. I ran into that with ex-T and ex-marriage counselor, where they tended to be really booked up, so extra sessions were rare. Though ex-T was able to accommodate me once, and it was really helpful.