A bit of semantics, but no, she was impaired by the environment she choose to place herself into. As I understand it, she wasn't disabled in her normal environment, the gravity of her species homeworld.
Look at it this way, if you hux were to put on scuba gear and go down into a body of water, would you at that point be "disabled?"
If I was just visiting, no but if I was compelled to live and work down there on a long term basis then yes, I would be disabled by the environment. Depends on your political viewpoint. Oliver's
Social Model of Disability promotes a perspective that the psychical impairment is not the thing that disables an individual but rather it is the society that does. Should society address those issues then you are no longer disabled by said society.
In many ways, there are countless alien cultures that are being disabled by human-centric environments in Trek. Usually it's the Federation cultural influence but in this case, it's the actually environment disabling an individual. That makes it more analogous to disability politics of our societies which is why I find it more interesting.
Strictly speaking, Melora wasn't disabled, she was perfectly normal.
Again, depends on your political definition. If, for sample, society bent over backwards - both in terms of environment and cultural attitudes - to enable wheelchair users total equality within society then they too could be described as "perfectly normal" as the factors disabling then have been removed.
All you have to do now is define normal.
This is why I applaud DS9. It isn't a perfect or complete exploration of the disability issue but unlike other Trek shows, it has at least looked at it from a non-paradise point of view that had previously been ignored. DS9 has a very good track record of looking at the utopia and questioning if everyone is experiencing it in quite the same way.