Girl confuses me?...?

well..my and my best friend..shes a girl..im a guy...after 6 years of being friends i tried to take the next step, and it failed, she said she was attracted to me and we even hooked up once but she didnt wanna throw our friendship away so i agreed, anyway, since then weve hung out a few times and gotten close as ever lately. Well today it seemed kinda wierd, she wanted to come swimming at my house but it started raining and i told her to come anyway and hang but she said she would another day. So i let it go and told her i was gonna take a nap and figure somethin out to do later and she never texted me back. Well i posted online that i was goin out to eat and out to a bar 2night and all of a sudden get a txt from her askin what i was doin, and i didnt have cell phone service at the time so i couldnt respond and when i finally did get it she had sent another one saying "Ignoring me are ya?"..seemed kinda wierd ya know...like she was pissed....then i told her my plans and she said "gonna get your mack on with the ladies 2night haha?".....i said "hopefully haha"...and then she just kept going on bout how tired she was and that she was going to bed and for me to be careful.... what im asking is why would she care so much what i was gonna do?? i mean..seems like she got kinda jealous or something....what was she thinking???....any help..