obviously something has come between you too, and the intial interest is gone.

Maybe you need to talk to her about it, ask her opinion and why she thinks its like this.

Then setup some ways that you could talk more, maybe find a mutual interest or teach eachother about your own interests, get to know her better and ask eachother more questions, there are loads of things to do if you think about it, but it might be wise first to figure out how it got like this, to stop you from ever getting into this situation again

Definitely sounds like you need to try and talk to her about it. The shyness should happen before you guys start dating, not afterwards. She might just be trying to get into her comfort zone with you, so she may be shy about doing/saying certain things. Just try your best to ease any anxiety she may voice to you about the situation. If it seems like the chemistry you had before is gone, then maybe you just need to go your separate ways. Definitely talk to her about things though. Good luck.

Let me know what happens

There's no challenge anymore now that you're together and so it's boring -- why don't you surprise her, kidnap her for a day and head out on a beach adventure -- or some place you havent been before. You can get lost together, laugh at how ridiculous it all is, and possibly spark something new

start talking to her again

Sometimes when the spark is gone, it's gone. You can still save it by working on your relationship, trying to discover things about each other, spending time together, talking about your younger days, what you like about each other, etc. It's possible that this one is just not the right one, however.