Ren - I would probably just say to her "each to their own, I don't judge you, so please give me the same respect".

But I would probably throw a few swear words in there too...

And FWIW - we don't co-sleep with our kids - but I never pass judgement on others who decide to - its not my place - and furthermore - none of my business!!

(ps... and this is why I don't have a mothers group - judgemental women $hit me!! lol)