Did your vet say what her idea weight is? I would try to keep her around that ideal weight. I found that multiple small meals helped keep my girl be less hungry. If she does have acromegaly, the extra growth hormone is causing her body to grow and she will gain a bit of weight as a result. My Neko had some Maine Coon in her, so a large breed anyway, but I told her she wasn't going above 6.8 kg. She didn't, though she wanted to.
Your vet will have to do what everyone else does, and send the blood to the facility that does do the test.