Welcome. Good name choice! Firstly I suggest you use the name's of these girls, twin cool and shy does not sound like a good use of nicknames! Secondly I assume you do know this girl you like's name, so I have some questions for you:
Do they always do everything together? Ideally you would talk to her whilst she's alone, less difficult for you and less embarrassing for her.
Is there a photography club at your high school? If yes, then why don't you ask her to join you at it, so you can see if you guys like it (your reason could be, you wanted someone else to go with you and give you an impartial view or you'd like her opinion since she also like's photography etc) ?
If there is no photography club, why don't you tell her you are thinking of starting one and would she like to have a chat after school maybe in the library with some books and your camera's about photography, ask for her input about starting a club, entering competitions etc. (to draw out shy people, speaking on a topic they like and asking them questions can get them talking).
What else do you know about her? Is she in any clubs? Does she do a sport? Please update us soon, we're all waiting to hear what she says!
All the best,