Need some help...

Every time my grandma comes over, she goes off about how Cookie is "a skeleton" and I need to feed her more.
This time, she threatened to take Cookie home with her if I don't feed her more.
My dad legally owns Cookie, but he actually agreed to this. I protested, saying how much easier Cookie has been getting around since she lost weight.
Apparently, they either changed their mind or were just bluffing, because grandma went home now and without Cookie. Or...she may still be planning to take her another time.

As much as I defend my uncle on the care of his dogs, I don't want Cookie in my grandma's or his care. (My grandma lives with my uncle.)
First, their dogs are free-fed, and while that seems to work well enough for Snoopy and Indy, I know from past experience that Cookie grows fat on free-feeding.
Second, they really don't pay much attention to their dogs unless they are being naughty or they want to go outside.
Third, they feed Purina.:

Either choice given to me, feeding Cookie more or letting my grandma take her away, is bad for Cookie.

I was thinking about having a vet check out Cookie's new weight so that I can prove that she is not malnourished.
My grandma will just say that the vet is crazy, but at least it would convince my dad not to let grandma take her and he would quit badgering me about feeding her more as well.

I know it won't happen, but I almost wish that my grandma would call animal control, so that when they see Cookie and say that she is the right weight, she might leave me alone.

Help?

Okay, the situation is more under control now, but I'm too lazy to update my post, so I'll give you a link to an update:
http://www.dogster.com/forums/other_posts.php?st=family&user_id=371549

Well, the vet said that Cookie is healthy and she is not starved at all. She did however, think that she could stand to gain about 4 pounds, but that was her relative opinion, and it's not going to hurt Cookie if I let her stay at her current weight.
Cookie's weight is now 72 lbs.
Compare that to last year's 94 lbs.
And to help her stay at the right weight, she recommended a suppliment to sprinkle over Cookie's meals. The suppliment also helps with arthritis (contains glucosamine) and digestion.
So, it's settled now and everyone is happy. Even my grandma.