I brought in a stray kitten from outside 6 days ago. Does her stool show that something may be wrong or is it normal?

I brought in a stray kitten nearly a week ago. She was wild, so of course it's taking some time to get her used to everything and she's been pretty stressed. Before you jump on me, I took her away from the outside & the wild because we have a lot of neighbors who let their huge dogs run around freely, and they've been known to go after neighborhood cats. I didn't want her to get killed.

Her stool has been runny & the other day there was some blood in it. I haven't been able to see if there has been any more blood because she uses the litter box & covers it up. My brother has had many cats & said that since she was stray and is getting used to cat food, and because of how stressed she is in a new environment, that could be the cause of it. Could it be? She acts fine otherwise, eats really well, drinks well, she's even been playing with a fuzzy little cat toy. She seems fine besides the blood thing. She doesn't get sick or anything. She does breathe a little quickly, but I'm wondering if maybe that's just normal or if it's because she's scared sometimes? Does anyone know?

I know I should probably take her to the vet just to be safe, but we just don't have the money to. Taking her to the pound would be no help because they don't take their animals to the vet and they have such bad living conditions for their animals. All I'm asking is if the blood could be because of the stress and getting used to cat food, and if the kind of quick breathing is normal or because she's scared.