Yes, take her to the vet for peace of mind and especially b/c she's an outdoor cat. There's no telling what she could pick up. Also, b/c she had collars on means someone has taken her in and she may be missing them. You shouldn't be angry about that. If my cat were outdoors and went missing, I'd be grateful if someone took her in. At least I'd know that she had been taken care of and fed. Let us know what the vet says.