Since your daughter is 2 and you say the Mom's child is younger and tends to play alone, I'm assuming the Mom's child is a very young toddler.
I'll bet this is a case of a new, first-time Mom who doesn't quite understand that a 1 year old's behavior is VERY different than a 2 year old's! She hasn't yet experienced her own child's exploration into parallel play that occasionally conflicts with other children (pushing, issues with sharing, etc.) As we know, it's not realistic to expect any 2 or 3 year old to easily share 100% of the time without issue. But this Mom does not understand. Her child doesn't misbehave (yet), and she thinks it's due to her "perfect parenting."
She's in for a rude awakening as her child gets closer to 2 and then 3. Is there anyway you and your friends could feel better knowing that she just doesn't get it? No...you are not wrong. It feels horrible to be criticized about your own parenting. I'm just not sure anything you say to this woman will make any difference.