To begin with, 1 Gb memory is very low whether running Tiger (10.4) or Leopard (10.5). You mentioned both OS's - which one is she running?
She should definitely upgrade her RAM whether or not she is Folding, especially if she likes to keep a lot of applications and widgets running. I checked over at www.crucial.com;
a 1 Gb SODIMM of DDR2-PC-5300 is only $14.99 (this is for the MacBooks with DDR2 memory) and a 2 Gb SODIMM of DDR3-PC-8500 memory is only $35.99.
Inactive memory is occupied by applications which are holding on to it until they need it again. As far as I can tell the only way to free it up is to quit the application (or widget)
You are already using Activity Monitor to check for cpu usage - click the "Real Memory" column header to find out what is using memory. On my machine usually the browser is the chief RAM user.
I'm not sure what to advise you about widgets that won't delete or which reappear on restart. These pages at the apple discussion forum may be helpful.http://discussions.apple.com/thread.jsp ... 3�http://discussions.apple.com/thread.jsp ... 4�
I always recommend smcfancontrol http://www.versiontracker.com/dyn/moreinfo/macosx/31029
for folding on Mini's and Mac laptops. It raises the fan speed for better heat transfer, and will keep the machine cooler.
Finally, THANK YOU for recruiting - Of all the things an ordinary user can do for the project that is probably the MOST helpful!