If you were a welcome face in a group they would not be acting 'weirdly' when you are around. Understand their behaviour and go away. The best you can do is to get on with your life and stop focussing on this one girl. Practice being relaxed in the presence of all people, get as many interests and outside interactions as you can. Then you will have something to talk about. When you do meet someone and the spark is there you talk to them and the feeling will be mutual, you will know straight away.
In this case don't load your expectations that 'you are the one' for her. If she was interested in you then the group she hangs around with would have encouraged her to see you by now. They have not, so don't force yourself onto the connection further.