some girls are just quiet. I am pretty quiet, I don't scream or anything, but I do talk and try to throw in a moan every now and then. lol. I try to express my pleasure physically tho, like an assgrab or digging my nails in, etc.

here's something you have probably never heard tho- some people are physically UNABLE to speak during sex. They're experiencing so much pleasure that their speech mechanism actually shuts down. It's rare to lose speech completely, but in it's mildest form (not being very vocal in bed) it is very common. Some people also can lose hearing or sight during sex. Sounds crazy, but it happens.

I wouldn't take her lack of speech personally, and I definitely wouldn't keep the "put sum effort into it" mentality. She is probably just enjoying herself a lot, and this is the way she shows it. She might not even be able to help it. However, if you really want to get her to speak up you could try buying a book that teaches "dirty talk".