Please do re-watch it, everybody. Merna clearly (figuratively) wipes her hand after shaking Noxie's. I thought it was out of character for Merna and especially weird for this particular movie.
At least there will be plenty implied.

I'm gonna look at this scene again and come back to this thread.
"Do you even remember what you came here to find?"

That is an interesting observation - I can't tell you how many times I have seen this movie and I never noticed this myself.
My take on it was, it was not a racial thing. I watched the scene closely and it didn't really look like she was wiping anything away. It looked like she was just nervously doing something with her hands (she may have been uncomfortable with new people, living in a small town?) and it also looked like she may have been scratching an itch or something.
Also, if you notice, she doesn't do anything with her hands until a few moments after shaking hands with Noxeema.