First, just know that virginity is not a medical concept, it's very subjective therefore virginity can have a totally different meaning from one person to another.
If you mean loosing virginity as first intercourse, not all women will bleed. It really depends on the person.
Bu if there's blood, then the amount of blood should not be gigantic, it shouldn't bleed a lot unless there's a big injury and it should stop soon after or the day after. I'd say max 3 days. If not, going to the doctor is strongly suggested.
The bleeding can come from the tearing of your hymen (but some women already have it teared from physical activities) but in many cases, the bleeding is due to lack of adequate lubrication and arousal, which causes microtears in the vaginal tissue. So the best thing to do to prevent that is to use a water based lubricant, gloves is you ever go into manual sex and to go slowly and make sure you're well aroused.
I don't think the bleeding is something to be really scared of or concerned about though as long as you're taking the right precautions.
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