why she takes so long to reply back ?

so i havent seen this girl for a long long time (i knew her from college) and one day she started talking me on facebook and we decided to meet and everything went alright. we said we should repit that and the next week i asked her if she wanted to do something on saturday. she told me of course and all thatt crap. the day of the "date" she told me she was busy and couldnt make it. i said it was alright. she didnt answer. five days after i sent her a "whats app " msg and again she didnt answer. now, a month later she replies back telling me that she had a dream with me and asking me how i was

She has someone