Is there away to tell if a female cat is spayed without taking them to the vet?

My neighborhood is over run with strays because my neighbor feeds them. Nice lady but a lot of them are sickly. And she doesn’t fix them, just feeds them. I run them off because they spray and I don’t want them near my 4 indoor cats when they go out in their catio. But this one will not go away. She’s so sweet and talkative. Really skinny but otherwise healthy. She’s not pregnant or in heat which seems odd for this time of year. I think she’s spayed and abandoned. I can’t afford to take her to the vet. I struggle with my pets vet bills. If she’s spayed though I think I won’t try to run her off anymore.