It is weird! Like you can rate your peformance as a parent based on how well your baby sleeps.
Try to let it go Sue - mums will do this. well, not all mums I'm sure, but mine did. I think it's a combination of trying to be helpful and getting a little bit defensive about their children making different parenting chioces to them. My mum stopped after a little while and has since come round - I hope yours wil too.

ETA - wow, your baby is an awesome sleeper!