I don't think you have the right to say anything.

I have on occaision done the same thing as that woman with my kids (albeit no-one was there to judge me). Each circumstance is different and we all make different parenting choices. If anyone chose to comment on a single aspect of my parenting based on an isolated (or even recurrent) incident, I wouldn't take it very well.

My firstborn had reflux and was an EXTREMELY unhappy baby for the first 5 months, the only way she would fall asleep was after 30min -1hr of screaming (regardless of if I was there or not). After 6 months her reflux got better, she got happier, but she would still never go to sleep until after she had a good long scream, not until she was over one. I couldn't stay in the same room as her, I was emtionally worn out, and it would just prolong the screaming/crying. I never discussed this with my mothers group or any friends, because I didn't want to hear them tell me their opinion.

My DS1 is still a terrible sleeper, but the CIO method never worked for him - so I have never done it with him.

My DS2 is a brilliant sleeper (so far - touch wood).

The only reasonI am telling you this is to let you know that you may not know the "whole" story, or even if you do, unless ahe broached the subject with you, you have no business talking to her about it, or telling her what she should orr should not be doing when raising her kids.