If you're a young mom, do MILs have the right to tell you how to raise your child?

I'm 23 and I have a 5 month old, he is the first grandchild in both sides. My MIL has been telling me all kinds of crap lately and I'm starting to lose it. I usually don't talk back mainly because I don't want to be rude but I'm losing it. She put me on blast today in front of my FIL's family and I wanted to tell her crap so bad but I just don't have the courage to speak up since we live under the same roof.