Help me!!!!!

My really good friend is bi, and she's recently been really almost flirty with me, like she plays with me hair and always sits really close to me and never leaves my side, also when another boy flirts with me she gets really angry at me and defensive about me... This is my first really good "BFF" friend ship and I'm not sure if this is to be expected or if she may have a crush on me!!! Please help

Much X thanks