[Marilize]

After their ears just stood up, they sometimes flop back down when the puppy's system takes a dip, e.g. when she is teething or ill. Most often, if the ears were up once, they will go up again.
At 3 months, I think she is a little too young to go to a groomer. She hasn't had all her shots yet and she may be susceptible to some disease. I'd wait until she has had all her shots.
To encourage the ears to stand, you have to trim the hair on top of them. It isn't that difficult - just get her used to the scissors and have her sit perfectly still. Decide on a command for grooming time and every time you pick her up to groom her, say the command. But make sure you say it AFTER you have her in your hands. If she moves, simply put her back in the same place. And after you are done, give her a treat.
Hope that helps!