I'm with the majority here.
Continue being a good neighbor, and take those guns out and enjoy them. In addition to thanking her with a picture of her gift in action, perhaps one will produce a target worth sharing*. Perhaps a small photo framed in with a nice target? I'd hazard a guess that she'd love to chat about the history behind those guns as well, give her a chance to do so.
No need to go overboard with the thank-yous and neighborliness, I'd guess that she didn't want someone to fawn over her, she just wanted to make a gift to someone who would appreciate it. So get out there and appreciate it! Restoration to serviceable condition may revise your estimate of value downwards, by the way.
As far as paying it forward, consider this a sign that you need to introduce a new shooter to the sport, if that Bearcat or model 77 are serviceable and reasonably accurate, they would be excellent choices for someone's introduction to firearms. Sharing that with your neighbor might be nice as well.
Selling them would be in poor taste, I agree that she might want to take a look at them sometime in the future, particularly if you've already mentioned restoration.
*(I might even get close enough to generate a good target ... just remember, even little old ladies may recognize powder burns)