You mean the drop of blood that they even said could have been there for weeks? No, that doesn't place her at the crime scene. They didn't place her in the bedroom, where Meredith was murdered, or the hallway, and I see no reason why Knox's DNA would not be found in any room that she lives in.
How did AK and RS manage to clean MK of their DNA but leave RG's?
In Meredith's bedroom, foreign DNA was found on the cuff of Meredith's sweatshirt, on Meredith's body, on her purse, on her bra strap and on her bra clasp. Four samples belonged to Guede, one belonged to Sollecito.
The blood in the bathroom and in Filomina's bedroom was directly connected to the night of the murder. Knox's DNA is mixed with Meredith's blood in Filomina's bedroom.
It's important to realize that DNA is not always found at crime scenes, so it's fortunate that DNA was discovered at this crime scene, as it clarifies who was involved in the murder ... we should be thankful for the expertise of the investigators that have worked hard to solve the murder of Meredith Kercher.