There were only small faint droplets of blood in her vulva area/underpants crotch. She would have had to have had blood wiped from that area after she was penetrated otherwise there'd be more blood.
Yes, there were drops of blood and she was wiped. It was seen and proved as a fact with the UV light.
But we do not know when it had happened. We also do not know how it happened.
Again, the bleeding that resulted her thighs being wiped could have happened at any time before her last bath and her death. We can not know for sure. It could have happened the previous night, christmas morning, at the Whites or after they came back home. All we know is that there was some sort of assault that resulted in her bleeding as much that it needed to be wiped away. We also do not know with what she was wiped because it has never been found and we do not know if it was someone else who wiped her or she did it herself. It is all possible.
If she was assaulted at the Whites party and that caused the bleeding and was wiped clean there, she might have had her original underpants on (the size 6s that were never found) and there could have been more bleeding to them. After coming home she, or someone else, changed her underpants to those mysterious size 12s. It would explain why there was not much blood in them.
She wasn't walking around in underpants big enough for her to pull up to her armpits. She wouldn't have been able to walk in those. And Patsy claimed she didn't notice them when she undressed JBR for bed.
She was a 6 year old girl, maybe left to attend for herself. I know my daughter "accidentally" took my socks after the wash and wore those not noticing that they were much too big until I pointed it out to her that those were not her socks. Sometimes children just do not think about it or just do not care. If she needed to change her underpants alone after arriving home from the Whites and, for example, was eager to go and play before bedtime, she could have just changed them in hurry, tucking them in her long johns so that she would not even pay attention to it. If that was the case, the long-johns kept the underpants up. IMO it is possible.
We do not know if Patsy undressed her for bed or not as a fact. Patsy did say that, but they said many things that they changed later or were just lying about.IMO she did not attend to her after arriving home from the party.