Why is she doing all this? does she like me?

here’s how we both are -she is very nervous, kind a shy and conscious when we meet (we meet once in a year) -on chat she is awesome friendly with me, always wants to know about me, teases me, flirts with me -if i dont message her for a long time, then messages me asking if i am very busy -always wants ME to be funny and humorous -whenever my messages are short, immediately asks me if am sad or tensed -once she asked me why i did not wish her on her birthday that too very angrily (that too after two months and never talked to me in that 2 months) -our main mode of communication is facebook, since last 2 years.

but when with her friends -does not show her best friends(all girls) me as her cousin (yes she is my maternal cousin) -behaves mean and talks negative things about me in front of them -shows them that she avoids me

Her friends are very outgoing and bold, while she is quiet type. her friends always try to influence her. i very well know that she likes my nature a lot, thinks i am a good and sweet guy, she knows very well that i never lie to her. i also know that in these 2 years, though for a few moments, she has loved me for sure. atleast has had a deep crush on me.she doesn not talk to guys much. i am her first guy friend and the closest one.we share many things with each other. she means a lot to me. I want to marry her. according to our culture its fine to marrry one’s maternal cousin (even she knows it very well). it may sound weird to you that i like my cousin but its fine in our culture

what up with this girl ?? Does she like me? Why does she behave mean about me in front of her friends ??

I am thinking of confessing my feelings to her

any help is appreciated. thanks in advance :)