Have you asked her about it? I'm a tiny bit vocal. My boyfriend isn't so much. Does that bother me? No. Sometimes I wouldn't mind him being a bit noiser, but we've talked about it and he's just not the yellin type
And that's just fine by me.
So basically, some people are vocal, some aren't. Some people start out being quiet to become more vocal. If you talk to her, maybe she'll give you some insight.