I'd like to point out that Gillibrand started as a blue dog and has shifted much more left ever since becoming Senator of New York. I only say that because I imagine Sinema having the similar trajectory.
But Gillibrand did that to fit NY's more progressive style of statewide politics. Or if you want to believe her take on it, because she met a lot of new constituents who she never heard about in her rural district. Does Arizona really present Sinema with an opening to make that kind of move? I'd be more worried about her moving further to the right...