Is cat preparing to give birth?

I know all the classic labor signs of a cat giving birth, such as:

nesting behavior

increased appetite in latter weeks

reduced appetite just before labor

clingy, seeking affection

pacing about, appearing nervous or particularly excitable

Thing is though is that this particular cat/kitten I had rescued from the streets 3 days ago and barely know her habits. She is very small, about 5 lbs, and is not a year old yet and did have a round belly and was starving. You could feel her spine as you stroked her from head to tail. I wasn't sure if she was full of worms and the round belly was overly round due to lack of nourishment, which made the belly look rounder or if she is truly pregnant. My second fear was FIP though I think I was overreacting since she began bleeding from the vagina just a few hours ago.

I drove her to a shelter today that was going to take her in, vet her and find her a forever home, though the girl wasn't sure if she was pregnant either and couldn't keep her since her facilities were not equipped for a pregnant cat.

I have her an appt with one of my vets on Thursday that help with my rescue efforts and T-N-R program I volunteer my time for, though tonight after walking away from the food bowl I noticed she left a small amount of blood and her feet are not saturated in blood but just enough where she must have placed her back paws into the blood while sitting and eating. I had a good look at her bottom and she is bleeding slightly from the vagina area. I set up a large trainer cage for her with a small litter pan and a box with a baby blanket in it then draped the trainer cage with a sheet to keep "my cats" from bothering her and to provide privacy. She did go for the litter pan and pee'd. There is no blood in the urine. She also left a nice little feces log which looked as if it was not covered in blood and maybe displays a bit of dehydration. She still has blood dripping from her vagina though and spots of blood are soaking into the blanket.

Someone please comfort me! Is this a sign that she is going into labor? I will definitely drop her off at my vet on my way into work in the morning to have her checked thoroughly if she hasn't produced a kitten by then, but I am concerned for her now since I hardly know this little kitty, where she came from and if she is truly pregnant.