I'll give you my advice, as a youngish female instructor/adjunct and as someone who is no stranger to inappropriate crushes.

I stay in contact with some of my undergrads after the semester is over. Facebook friends with some (they friended me), get e-mails now and then. I've had coffee with a couple. I became good friends with one female student who was around my age. (The age gap is not to be underestimated here.) However, as someone who is partnered up and 0% interested in dating one of my former undergrad kids, if I get a hint that a student has a crush on me, I quietly drop contact. I do not want to encourage that.

Perhaps you'll be fine remaining in contact. But I suggest that if you find yourself continuing to ruminate about this woman and spending your mental energy on that, you drop contact. If you're stuck on her, that means you're not spending time and energy on appropriate, healthy, real possibilities for relationships in your life. In my experience, any time I have an inappropriate crush, I have to stop feeding it by getting the person out of my life. It's sad at first, but it stops the unhealthy cycle. This is a lesson that I wish I had learned a decade ago. It would have saved me a lot of anguish.

Wishing you the best. Congrats on graduating; I hope you're acknowledging your accomplishment! Be proud of yourself.