I've had this same experience. You can: continue to try to contact her and tell her you need help (and set up a time to work together on Prezi, preferably not Thursday night), or do your part in a PowerPoint format, tell her that is what you are doing, and send it to her to either add her part or to switch it all over to Prezi; or if you know all the info, do the whole thing in PowerPoint so you are ready come Friday.

I had a classmate send me her part of a presentation at 4:30 am the day of the presentation. I had a classmate do nothing--then ask for a copy of my notes the moment before that presentation. One thing I have learned. Some people in college have no shame.

If need be, copy the professor on the emails you are sending her.