I suggest you being in touch with her in the motive to learn more about the subject that's common to you both. I guess this will prove your interest to join the lab to her. You don't need to be in constant touch again.
Find something interesting you can discuss on that's on par with her level of expertise. It's hard to find such point of study. So take couple of months, grow yourself in the subject then ask her a couple of questions about her views. If she doesn't answer, just send one and only one follow up email.
Let things take it's own pace. She might not reply but she will surely see your growing interest. Hopefully, you might get into her lab next time otherwise you still learnt a lot more than previous year.
Check this course if you want to learn a few pointers on writing emails.
https://www.coursera.org/learn/professional-emails-english