Hi AlisonLouise, I would get her to a vet as soon as you can, especially if she's squeaking and noticeably showing pain. Blood from the genital/ anal region could be caused by a urinary tract infection or possibly something more serious. She may need antibiotics but only a thorough check over by a vet can confirm that.
Aside from the blood on her that you saw would you be able check for any other traces of blood in her bedding/ toilet area etc without upsetting her? What type of hamster is she btw? The squeaking could possibly be unrelated to the blood, she might just be a talkative hamster... But does it sound like an upset/ agitated squeak? I would keep an eye on her and see if you can notice any pattern around when she does squeak, like you said: see if you can check if she's squeaking when she wees...
Maybe try and give her a check over yourself. While you're holding/ playing with her tonight check her for small cuts that could of possibly caused the blood, gently stroke your hands over her to check for lumps and bumps (in this case I would especially check her belly and sides). And if she is active and happy then let her do her thing like normal tonight, maybe give her her favourite treat and again keep an eye on her until you can get a vets appointment.
Keep us updated on how she's doing, it's easier said than done but try not to worry too much, you're doing the best for her