Don't say anything. If she isn't supportive of your breastfeeding, don't mention it. Any questions about baby's eating habits can be answered with "fine", "great appetite", "doctor is pleased with gain" and left right there. As to the older child nursing her dolls, it is normal for children to mimic the adults they are around. My ODD used to pretend to pump with me, and has nursed just about every toy she has, as well as wanting to nurse her sister. YDD, since she also spends a lot of time at daycare and sees bottlefeeding, will bottlefeed her dolls, or ask me to breastfeed them every now and then. Both totally normal and healthy, and so is your dd. A good answer for your mom is "she is fine" and then move on- direct the conversation in a more neutral direction.
And to answer your question as to whether baby is getting enough- count diaper changes. If you are changing six or more diapers in a twenty four hour period then baby is getting enough :)
My MIL scared my son to death of Harry Potter. We had all the movies at the time (years ago). He crawled into a ball when I said you want to watch Harry Potter. He would watch 2 a week. If you can't trust this person, you can't leave your child with them, regardless how much you want to.
A year later I got rid of the Potter movies because he never would touch them again after she did whatever she did. It is a shame that adults go to such lengths with babies because they don't approve of things their parents are ok with.
My mil fussed my daughter for playing pregnant/ breast feeding, so now when we catch her, she shuts down. I tried telling her it's ok. It doesn't bother us, but it's too late. Damage done!