She sounds like a typical retired greyhound to me I took my first greyhound to a dog park and she just stood, looking at me like "can we go now?" She would walk beside me if I walked around, but that was it. Many greys are what we call breed snobs. They aren't familiar with other types of dogs, and many just aren't interested. I'll bet if you got her around other greyhounds, you would see a different dog Like other dogs, some individuals are more high energy than others. I currently have a gimpy old man (11.5) who loves walks and would go far longer than is good for him if I let him. I have also had greys that are perfectly satisfied for one slow paced 20-30 minute walk a day, plus a few ambles around the yard.
If she is healthy and a good weight, I'd say she is fine, just, as you say, lazy