Compared to the people I see on a regular basis Ashley Graham looks big to me. I wouldn't call her obese but I would say she's big. I'm not sure she would be my role model for what a healthy weight should be but from an aesthetic perspective I think she's very pretty and pleasing to look at, she's in proportion and she has a curvy body... I think that's what looks best regardless of how much you weigh (although there's obviously a thin and fat threshold to that... there's nothing attractive about anorexia or morbid obesity). You can be super skinny or thin and fit or large but if your body is one line/shape up and down I don't think it's as aesthetically pleasing.
From a fitness/health perspective I wouldn't know if she was healthy or not without knowing other metrics. Weight alone doesn't give an accurate picture of someone's health but from my experience of exercise I have a hard seeing how you can be at that weight and enjoy exercising, the more you weigh the more of you there is to lug around, the more stress it places on certain body parts and the harder certain exercises are so I'd like to know how she maintains her health and fitness. I looked on Ashley's social media pages and watched some of her clips where she's exercising... In one clip she was running on a treadmill but she was running pretty fast, it's looks like it was done for show because I can't see how she could have kept up that pace for long and some of the other stuff... hmmm I don't know.
If she's fit and healthy, that's great. She's lucky with her body type, carrying weight on your legs and butt supposedly has a lesser impact on your health... so perhaps she's as healthy as a horse and has been blessed with great genes that make it easier to avoid all sorts of problems.