Actually, I am an English speaker, live in the United States, and pronounce the lovely name Marcella as mar-CHELL-la as well. I am not even Italian, either. *shrug* It sounds prettier that way.
A mean person? I highly disagree. I think Marcella sounds exotic and very beautiful. Different and uncommon too, which is always a good thing. Definitely a good feminine name to consider.
I was named Marcella after my great grandma. I was mostly referred to as Marcy, but also Celly, Cella, Marce. Now that I am in my 30s I go by Marcella a lot. I have gotten a lot of compliments when I tell people my name. As for someone thinking it sounds like the name of someone mean, well all I know is my great grandma was one of the sweetest people I have ever known. And I don't see myself as mean. But maybe we just are different from the rest lol.