I don't believe it is true.
McDonnells report refers to them (I think) but states that he is unsure if they were taken after the body was cleaned. I'll have a look again to see what it says.
I also think that the defence would have questioned this if it were true when they were advancing their ritualistic cleaning theory.
I suggest you do a lot more reading of documents on here as that will clarify what I say.
The ritualistic cleaning...quite reasonable in the light of Sheila's schizophrenia and something that could be predicted.
This would have been after she killed the other 4. Cleaning herself up and any clothes she may have worn at the time if she had not been naked or near naked when carrying out the killings.
When Sheila was shot she and her clothing was clean...though of course the nightdress could have been put on Sheila after she was shot in my view until I can find anything firm to state either way as to whether the nightdress was worn or not...I shall keep that option open.