If there was Amanda's blood in Meredeth's room, that might have far more meaning because my understanding was that they did not spend much, if any, time in each others rooms.
The whole issue can the whittled down to this:
There simply is no evidence of Amanda or Raffaele in Meredith's room. None. If there had been "mixed-blood" found somewhere else in the cottage, that may be a sign that Amanda was once in Meredith's room at a suspicious time, but that would be met by the fact that none of this was found in Meredith's room.
"Mixed blood" is something even comments-sections-flooders like Harry Rag has dropped after years of making this claim.
Judge Massei in his motivations report, even in convicting them in 2009, simply ignores the issues inherent in this. He simply ignores that there is no forensics in the room you'd expect - especially since Massei conjectures that the "biological matter mixed in with Meredith's blood" found in the bathroom was, for him in his imaginings, the result of Amanda cleaning herself vigourously of Meredith's blood
in the bathroom - Massei simply ignores that he's made no mention of how that blood got onto Amanda, or why if she'd been covered in blood in Meredith's room, none of that is forensically evident
in Meredith's room!
In short, nothing about Massei's imaginings/reconstructions or assertions of "mixed blood" actually make sense.
Further imaginings are required. Guilters, before they vanished, used to claim that Amanda had been hit in the nose and bled from there. Yet no forensics support that. Then they claimed the mark on Amanda's neck was either originally a gaping wound, or at least a source of blood. This requires they ignore the police-evidence collected at the time of Amanda's arrest, that clearly support that mark as inoffensive and more than likely a hickey.
The imaginings, both online and even more stupefying in the judiciary prove that there is no mixed-blood. Or else: why the imaginings?