Girls need advice please?

Hi, so I'm in school in year 11 and I'm confused about this girl. In year 9 we used to talk and flirt a lot and I know we were both really liked eachother. So year 10 comes and because I have much on my mind and because she suddenly stopped using our bus I found it hard to talk to her and I suppose forgot with so much going on. I noticed she still used to look at me now and again but it died down through out last year. But I did talk to her now and again and for the next couple of days she would seem more interested but I didn't take much notice for my own reasons. Well couple of months ago year 11 starts, I still notice the looks etc And I thought I was such a fool because I should have took more notice in year 10. 2 weeks a go I saw her in a corridor and we both smiled and said hello, for the next few days she really tryed hard to get my attention. I was taking notice but I'm a shy person. Last week I talked a little bit, bit just didn't know how to respond to her talking to her friend in front of me a few times. I hoped she didn't take it as me ignoring her, I tryed talking a bit. So during this week I've openned up and talked some more but the looking/staring/attention stuff has decreased in just this week when I HAD talked. I didn't even catch her eye in the last 2 days. It confuses me as I'd expect her to respond back after liking me so long. This is really weird she liked me so much just a week or 2 ago! Do you think she likes me? If I become friendly do you think she may start flirting again, I still like her. What do you think?�