Well if she's liked some guy for a year and has done nothing to initiate then it's possible she likes you too and is acting similarly. People have their patterns. Her looking at you and becoming jealous at your attention towards others indicates to me that she likes you, but doesn't know how to deal with it. If I were you I'd start dating other people and move on. She'll realize you aren't around forever then and maybe actually make a move. And if she's too afraid of rejection she'll become much more clear in her feelings towards you by becoming cold/withdrawn and then maybe you can just ask her what's up and see how it goes. This way you can determine if she likes you and if she doesn't you'll be dating someone new to have fun with. Win win.