I was attempting to find some tips online as to how to nicely put it when you have a family member like mine who you love and respect but that does not listen to the restrictions you have on your child's diet. It's really hard and uncomfortable to have to be that way. I love and respect her and want her to have all the access to Bella that she wants and value her opinion and tips on mostly everything, except with my child's eating habits. She is very old school and believes nothing has changed since she reared her own children, and oh boy have they! You will probably end up being the bad guy and bite the bullet like I did and have to really put your foot down, even mentioning not bringing your child around as much, but hey if it's for Bella's safety and health there isn't anything I wouldn't do.
I found an AWESOME article written by a now-Grandparent. http://www.thetranquilparent.com/detail/whose-rules-rule-parenting-and-the-role-of-the-grandparent/
I wish all of you the best of luck if you have a family member who doesn't listen to your parental wishes, and I hope you can all find a common ground because family and love are the most important things to have in your child's life and they will forever benefit from what they learn from those around them.