Questionable friend?????

My friend (who's a 15 year old girl and my ex-classmate) keeps making dumb excuses lately when i invite her to hang out, even though she lives right near me. Some of these excuses are obvious lies. she never really tells me anything actually serious about herself, even though we've been friends for a few years. before we spent time together like there was a schedule: she comes then suddenly can't for a week or a two, then again. this has been going on for almost a year and i'm getting real pissed off at her. what is this? should i tell her to get lost?