seems like she is enjoying her time with her bf....
so why dont you give it a try? go out.. hang out withyour firends and give some girls a chance to get to know you and you get to know them as well.. you dont have to have an exclusive date, you could go out on group dates if you feel awkward doing it for the first time. it's one way of knowing how you truly feel. plus, sometimes, you meet great people in situations and places you least expect. you just need to open your eyes more to see the big picture.
just like you not letting her know how you feel when she was still single... you will also never know what's in store for you unless you take the first step.. try... get to know some girls.. who knows?:)