Mrs. Peach was mentioned and drawn in Tales From a Not-So-Fabulous Life by Nikki. She is often called a sweetheart. This is because she had done many good things for them, such as warmly welcoming Nikki to the LSAs, telling the LSAs about an upcoming trip (so they can prepare), letting them use the library for meetings for the Halloween dance committee, and allowed them (or possibly not noticing) to goof off and have fun, yet still do their job (although it's possible she doesn't know what they do).
Mrs. Peach is a kind and caring sweetheart, as said by Nikki. It is mentioned in the 1st book that she gives them humongous double chocolate chip cookies with walnuts almost every Friday.
Throughout the books, Nikki has not described Mrs. Peach's appearance. All that was shown is that Mrs. Peach wears glasses and plaid skirts. She is elderly and has short layered hair.