well, you obviously can't tell it so across-the-board-ish, some shy girls are cats in the sack, while others are very self-conscious.
Just be gentle and take it slow, she might take a bit longer to get into the mood, try to be a bit more romantical instead of rough.
Give her the impression that you care about her issues/pet peeves (or do care! even better), like "omg, the light is so bright, I can see my fat rolls." or something and of course try to help the situation to make her feel comfy.
If she's shy then give her a nice compliment during a tender moment. If she's shy she might not realise how fit she is, and she'll really appreciate it and so become more comfortable and more likely to come out of her shell a bit, both sexually and emotionally.
Conformity before conscience Uniformity before faith!
To infinity and beyond!
"the reason i took drugs in the first place was because ...i was confused.
it's all become clear since" -Rolly.
Just as it is true that a stream cannot rise above its source, so it is true that a national literature cannot rise above the moral level of the social conditions of the people from whom it derives its inspiration-James Connolly.
If she won't shag you next, she probably doesn't feel comfortable. Is it her first time? You should respect her boundaries and wait, if you think the relationship is worth it... Or you can get her really drunk... Or maybe just explore each other a bit.
Life is like riding a bicycle. To keep your balance you must keep moving.
Fuck with her mind!
Keep conversation topics pretty flirty and plant subtle ideas in her head, good eye contact & smiles.
Learn where her 'spots' are, for example - lower spine, behind the ear, shoulder blades etc I'm sure you get the idea, there are bound to be a few spots that give her that tingley feeling which is good