I'm just going to go on a little tangent, so bear with me. Those of you who have seen me on the threads know I like to infodump most about two things - forensic science and serial offenders. I'm going to talk a little about the latter.
When talking about serial offenders, we talk about signature behaviours, things that aren't 'necessary' to commit the crime, but fulfill some need for the perpetrator. We know most about behaviours of men in sexually motivated homicides, because those are the ones who have sat down with profilers. I think it is important to note that this kind of postmortem washing/grooming is a known behaviour. Bundy's probably one of the most well-known to have engaged in it - even shampooing victims' hair and doing makeup - but he's far from the only one. Postmortem handling and engaging with the body doesn't have to be overtly sexual or violent to meet a desire in the offender. It's all about having total control. Dahmer did it, Nilsen did it, and probably dozens of others less well known.
Engaging with grieving loved ones and prolonging their pain is also a known behaviour. LISK (RH), Joseph DeAngelo, and Larry Gene Bell all rang their victims or their families. Other murderers have happily been the 'strongest support' for shattered parents or loved ones, holding hands, arranging funerals, soaking up the fallout of their actions like sponges. I've seen this especially with some sexually motivated child killers who chose to attack children in their social circle.
I would say that in this scenario - if guilty - there really are strong parallels to other serial offenders in her need to control and intrude on postmortem ritual and, in particular, handling of the body (bathing, dressing, posing for photographs, taking hand and footprints, cutting locks of hair).
MOO