how heavy? Sorry if this is TMI but is it normal if heavy menstrual flow ? can it be managed with extra absorbent pads or tampons? Answer yes then wait and see GP, answer no, phone OOH. In either case unless you think she is at risk, i wouldn't be rolling up at A and E on a saturday night.
I`m no expert but if it was me, I would be inclined to watch the situation for now. If the bleeding becomes severe I would go to A&E but anyway, I would make plans to see a GP or midwife in the morning.
She won`t get blood poisoning. You just need to keep an eye that she doesn`t bleed too much because the risk with that is that she could go into hypovolemic shock. Hopefully, that situation won`t arise though.
Very unlikely provided she follows ordinary hygiene routines. are any of her friends health care trained? the risk is if its a haemorrhage and not menstrual flow which i why i asked about volume.
Here is a useful if scary leaflet, i would suggest that you read it but not pass it to your daughter.
That is the bottom line.....so providing that the pain does increase to "cramping pains" she should be fine.
If it is a complete miscarriage then the bleeding will settle, but if the bleeding continues with pain, then she should see her GP as iy may indicate an incomplete abortion.