My mother is always trying to convince my son I don't love him....rant.

I've never had a great relationship with my mother, she's always been verbally/physically/emotionally abusive towards me while my older brother (by 10 months) could never do any wrong. Since I've had children I've tried to get along with her. She favors my 8 year son because he's a boy plain and simple, and rarely has anything kind to say to my daughter (4). Today she came to visit and my son tends to show out in her presence I corrected him on the fact that he didn't do his homework after he lied and said he did and she went on a rant. Telling him that I don't love him, comparing him to my four year old and saying she was going to get custody of him because I didn't deserve him. She always does this and I only tolerate her in small doses because my son loves her but it's so frustrating. She and I ended up in an argument and I put her out. I hate that she puts that stuff into my kids head and causes chaos in my home. I love my children equally and understand that they're different people but she's always comparing them. I know she will do the same once my new little girl comes and I don't even want her around.