SIL issues

So I don't get along well with my SIL(sucks I know) she constantly telling us how to be parents and when we announced I was pregnant with our third she text my husband and asked him what he was thinking(mind you she 19) we been together 8 yes and have 2 other children. Just frustrating because my husband doesn't want me to fight back to just listen and understand things they are telling us. But I can't anymore.