TinyTink, you lovely lady, there’s lots of good advice here. At the risk of simply adding more I would combine three.
1. Several people have advised you to ask her to repeat the comment. Excellent advice, followed by the advice of agnurse on page 1.
2. If she is hard faced enough to repeat what she said, you can tell her to apologise. Difficult I know, so
3. Again lots of people’s advice: practice in the mirror.
Finally, the real power struggle winner, take your baby and say, ‘You can go now’. Those 4 little words show that you are calling the shots. Your house, your baby. Open the front door and stand there. That one is really hard to do but powerfully effective.
Be prepared, she will complain to your husband. Have the conversation with him so he’s ready when she does.
He needs to be able to tell her that you love to have her at your house but you won’t be insulted in your own home. You’re looking forward to her next visit. You want to have a good relationship with her and so on.