In the Exhibits and Findings (http://www.themacdonaldcase.com/html/exhibits.html), Exhibits D48NB, D49NB and D50NB refer to the Type O blood on the floor beside Kristen's bed.  Excerpts from a couple of the Notes for those exhibits show the following:


July 5, 1970: Pre-Article 32 defense questioning of Robert Shaw (CID)

Questions by CPT DOUTHAT:
Q  The type A blood beside the bed, north bedroom, do you have a theory as to how this blood got there? You mentioned a moment ago you think the child may have fallen out of bed?
A  Either fallen out of bed -- you can see the bloodstain down the side of the bed. This is why I said to you I think she was stabbed in the chest first. Well, of course because of the finger now, she either put her hand there or it was there and she was stabbed in the chest. Now if this is the case, then she was stabbed and moved so that she bled down the side of the bed and onto the floor. Again, she could have fallen out.
Q  Or could have hung over the side of the bed?
A  Yes.


June 26, 1973: Excerpt from U.S. Attorney McNamara's memo to the DOJ

". . . There is no evidence that Kristen was in any other location but her own bed while the murderous activities were taking place around her. There were large pools of blood (Type O - Kristen MacDonald) found on the floor adjacent to her bedside, and these blood pools were not in a location where they would have been if she had not been picked up and held over the side of the bed. This activity then took place when she was probably receiving the stab wounds to her back and while she was bleeding heavily from chest wounds already inflicted." [end quote]


The government's theory was that Kristen never left her bed, but I don't think anyone will ever know for sure whether Kristen was trying to hide under the bed before her murdering father came to attack her..