i jus dnt understand my ppl come in contact with

its this girl who i recently stopp talkin to..i dnt understand i mean we are best friends and everything you know skool buddies u knw we were close we shared everything together i mean we were not together but we were close just like an relationship we provided for each other u knw talkd thru all our problems our bad times and all and now all of the sudden her phone is off which she explained to me and everything i let her older sister to to call me cuz she had my number in her head and neither her or her sister wunt return any of my messages or anything we were suppose to meet up last week i went to my high skool i graduated from and were suppose to chill after skool and afta sittin there waitin for bout 3 hours she txtd me frm her friend phone sayin ''oh baby.. oh..i tried callin you'' and etc. and this is like the 3rd time she stood me up and she once promise me she wud never let me down and she did 3 times and she didnt have any skool wrk to be done cuz i tlk to her mom and stuff me and her mom are kool also she likes me cuz i have respect for her daughter and stuff anywayz i sent her a message 2 dayz b4 vday and no reply or anything and i jus check it earlier and it said she hasnt read it and i go check it now it says she read it and ive been leavin her comments and to see how she doin and etc but no reply so so ever since i got stood up those times our relationship (Friendship) is basically failing i even made efforts to visit her at skool and look around for her but nothin you knw so we dnt speak anymore i jus dnt get it though