Vent away. This is not the craziest I've heard of, but not the most normal, either. Some women are simply like that--your mother or someone else's. I shudder to think of what people say of us! I nursed for about a year with each (which my mom thought was weird after 6 months, but my Father-in-Law apparently thought was awesome and was bragging about). My mom is the weird one, but she lives on the other side of the U.S. I've made certain topics off-limits (namely my husband) but I pretty much don't see my family. Travel is not affordable, etc. We see my in-laws infrequently also because of work schedules and living 2 1/2 hours away. We are probably lucky to get together once a month. It sounds like she mostly just gossips and complains and criticizes. It is annoying, but not unheard-of. My husband's grandmother apparently complained a lot about her daughters-in-law who nursed instead of giving formula, but she adored her grandchildren and was a wonderful grandmother. You could just offer information on child development, change the subject, or say you don't like to criticize other people. If she close to you, this does not sound like too often for seeing her. We always wear hand-me-downs (sometimes my favorite outfits for my kids had been through several other children). Unless she has a negative and damaging relationship with you or your child, I would just try to ignore the comments for now.
As a side note, my husband hates my mom (really hates her--it annoys him when I have any contact with her, etc. and he resents that she does not call for our children's birthdays, for Christmas, after they were born, etc. even though he called her from the hospital). We finally just don't really talk about her. I believe she loves me and my kids, but it is more comfortable for me to have less contact and fewer opportunities to feel hurt about something. We've had email drama (my family, apparently, was shocked that my husband and I read each other's email unless it is about something we're planning like a gift or other surprise), we've had in-person drama, phone drama, everything. Good luck...