You want to build a good relationship with her. That’s why you cared and asked here. It’s sweet.
I think you’re in the US. Then, in my opinion, treat her in the same way as you do to other people. When you want to pay her respects, pay respects in the same way as you usually do. I assume that you want to show your affinity to her and Japan, and calling her Senpai may be one of the ways. But maybe, she takes it as a sort of bias, because being an outsider is not fun thing in general. I hope you will get along with her very well.