I find people that make comments like that have very low self worth. She's at home on mat leave and sending her kid to "socialize"? If she really is as smart and confident she would realize that there are several, less expensive ways for her child to socialize where she can be present and part of her child's experience. She could go to a drop in gymnastics class, or swim lessons! She could go to a playgroup and sip some coffee while her kids play. I am betting that she is having trouble managing two, and therefore is farming out her eldest's care to you while on mat leave. Therefore she feels the need to belittle you in order to make herself feel better about that decision. The fact is, parenting is a basic skill set. I find the ones that don't have it together are the clients most likely to make belittling comments to us, particularly if what we are doing, works.