<human>: Condense the text into a few key points

I met her for ther first time on 27th December 2012, we were in a pub with some mutual friends. Since the beginning I thought she was an interesting girl, but I did nothing because one of those friends already had a crush on her.
A few days later a friend of hers asked me to go out with them together and I accepted without any doubts, so since that day we started to go out all three together.

In February 2013 I started to like her a lot, and we often frequented eachother from a month, always with this other girl or sometimes with other people. We used to talk a lot, in reality and by chat also, but I never told her that I liked her.

The situation is still the same, I still like (maybe love) her, but I never told her.
The main problem is that currently we still frequent eachother, but it's not like it was before, we are often with a lot of other people and we barely talk and never chat(I don't know why we don't have the same contacts as before).
Another big problem is that she is a really closed person, not in the sense of introverted or shy, but it's really rare to hear her talk about herself or her problems. She also often refuses physical contact.

So I really don't know how to behave in this situation, I'm trying to persuade myself on telling her tomorrow, but I need motivation and advices, thanks.
(Never had experience in this subject, never had a girlfriend or asked someone out)
<bot>: I like a girl since one year and a half, we barely talk and she often doesn't even consider me, how should I tell her? (Need motivation and advices)