It may be slightly harder than if you had a younger pig as when they get older, they are more set in their ways. However, repetition and positive reinforcement should probably do the trick for training her (pun intended.) I trained my guinea pigs when they were about 2.5 years old :) And no, she shouldn't be too weak to be taught, but they normally can't sit up for more than a few seconds. At least, my lazy pigs can't! :) Gotta love cavies. Hope this helped!