Party games are good fun that the whole family can enjoy. Picking one of these might be your best bet at introducing her to gaming in a casual, enjoyable fashion. Whatever you do though, make sure it's not Wii Dare unless you have some latent Oedipus complex.
The game revolves around a lot of mini-games, like most in the genre. However, they're intensely sexual. Some will require you to bend your mother over your lap and slap her backside, others will leave a controller dangling between your faces while you kiss it. We're not against a little casual fun with relatives, but this takes it to a whole new level of incest that you probably want to avoid.