The spot is huge, clear, and has no smell. As far as we know she doesn't squirt. We want to know if this is normal. Should she go see a doctor, or is this okay?
It seems like the wet spot could be sweat. Your girlfriend may have hyperhidrosis, if so, it is natural to sweat excessively during sex. But of course it depends where the sweat is coming from. It usually accumulates under the anus, between the gluteal muscles; especially if she is overweight.
Although, if it is coming directly from the vagina and has no odor, it would seem natural.