Sheila would wash herself because she was committing suicide and presumably wanted to look her best when found or something like that. Bear in mind a washing theory was propounded at trial by Professor Bernard Knight, a very eminent pathologist. It's not as if I've just thought it up.
Reference has been made to Sheila having poor hygiene, but it's just an anecdote from one of her previous employers. If you're saying she was unkempt out of habit and wouldn't have cared, then why did she bother attending to her nails and hair? The pro-guilt account of Sheila seems to be a bit muddled and lacking in overall consistency, as if intended to suit the answer needed at the moment.