at her age, weights are even more critical than ever: weight-resistance exercising has been shown to prevent, slow down, or in some cases reverse osteoporosis and will help protect her from broken hip injury, which is one of the most common ones among the elderly.
start her off with those pretty, pouffy pink weights - 2 and 3lb jobbers.
start her off gently - squats, chest press, single-arm rows, overhead
shoulder press, bicep curls, and
tricep kickbacks to start. i wouldn't do the pushup thing. if she won't use even the pouffy weights, hand her soup cans.
reassure her she'll NOT end up looking like schwarzenegger even if she tried because if she did you'll ding her upside the head for doing steroids.