I wrote a couple articles on purgatory a few years ago that might help:

http://www.aboutcatholics.com/life_in_c … ory_bible/

http://www.aboutcatholics.com/life_in_c … purgatory/

Here is an ancillary article that may address other conversations you might have with your daughter (depending on her brand of Protestantism):
http://www.aboutcatholics.com/life_in_c … salvation/

Now I will step aside and let LARobert give you a more thorough answer.