What should I do about this volunteer situation?

I have a volunteer research assistant who is just fantastic. I want her to stick around for as long as possible and to enjoy her time working in our lab.

Unfortunately, parking here is quite expensive. She brought the problem up and asked if there was anything I could do about it.

After contacting the parking people, there is really no way around it. The only thing I can think of is that I could pay for her parking myself.

If you were a volunteer, would you expect free parking? What should I do?