Sounds like either she was stressed while you were gone and started overgrooming as a result, or she picked up fleas at your mom's house. If I were you, I'd pick up some Advantage or Frontline from your vet (do NOT use retail store flea products. Too many of them are highly toxic). If that doesn't do the trick, then speak with your vet about the problem. You may need to put an e-collar on your girl for a while so that she can't reach her tail and will, hopefully, break the habit.
Laurie
Laurie