She wasn't in the shower, she was going pee or poop. If MS was 6 and had to be watched SO closely, that Rebecca shouldn't have gone to the bathroom, he should have had 2 nannys to watch him when he was there, in case one nanny had to go potty. Sheesh. She did not kill MS. She is not guilty.
Apparently being millionaire's girlfriend ain't all it cut out to be. She was expected to babysit (why no nannies/babysitters?), her sister apparently cut herself cleaning up glass (no housekeepers?) and we haven't heard about any household staff present.