It took a little white to find on Frontier's web site, (apparently typing in "name change" in their search box won't find this information) but here's their policy on name changes:
Can I change the name on my ticket?
To protect you, all our tickets are non-transferable. In other words, they're only valid for the name specified on the ticket.
Oddly enough, you can for $35 change names on award tickets, just not on regular revenue tickets.
You can find the information here:
http://www.frontierairlines.com/fron...ations-faqs.do