Personally I wouldn't try to get her "help" based on those facts. I'd continue to be her friend, because she needs to not be isolated - and people like that tend to get isolated. Then I'd talk to her about her ideas in a non-confrontational way. Just ask her why she thinks the mom is poisoning her animals. Not like a lawyer or a cop asking her to provide evidence of her allegations but just like a friend chatting with a friend. If she says the kids are spying on her, you can say mildly, "It just looks like they're playing in their backyard to me." If she insists they're spying, ask her how she can tell, what would they be doing if they were just playing and what are they doing that indicates spying. If she gets too angry, just drop it. You don't want her to get paranoid about you, because then she won't be open to talking to you. You'll have gently introduced the idea that her perceptions may be wrong. Don't do it too often or try to shove it down her throat. That won't work.

If you remain in regular contact, you'll know if she becomes a danger to self or others. Then you can do something about it. Unless that happens, she just has odd ideas, and if her husband is making sure she has food and shelter and neither of them want psychiatric help, I'm not sure there's anything you can do.

Paranoid people are just really fearful people. The fear attaches itself to lots of random things. You don't want to do things that increase her fear. You might also try to distract her if she becomes obsessed with these topics - preferably with some enjoyable activity or conversation. She needs something positive in her life.