Seniors fall -- fact of life. But if you fall with an aggressor after you, think about using your feet and legs as weapons.
An aggressor can't protect his legs very well. And your legs are much stronger than your hands or arms. I've seen videos of people on the ground just thrashing their legs around, not doing anything useful.
One thing you might be able to do from the ground is try to kick their knee so it bends in the wrong direction. Pointy-toe ballerina kicks are mostly useless, so use the firewood-stomping method instead. Kick out flat-footed, at the side or front of their knee --- it's really painful and often incapacitating.
If someone grabs you from behind, the victim often instinctively tries to escape by moving forward, which usually doesn't work, as they're expecting that, and they're ready for it.
If you've got a solid object in front of you (a wall, post, rail, car, etc), reach out with one or both feet and use it to shove yourself backward as hard as you can.
This might also work if a man grabs a woman by her hair. Also try reaching behind you and grabbing his family jewels. Got fingernails? Dig in!