What should I do? Please answer?

So, my friend and i are pretty muc best friends we hang out all the time, we went to the mall yesterday and we couldn't have a sleepover because i forgot to ask my mom. So that night i asked my mom if her and i could have a sleepover tomorrow she said yes. so i told my friend we could have a sleepover the following night. then the next morning my mom told me shed rather have my friend sleepover sometime next week because she wanted to relax with my dad and i(which i dont understand how its not relaxing when my friend's over its not like we go crazy). but anyway i told my friend we couldnt have a sleepover bc my mom said no and i was really sorry. i didnt tell her why because i didn't know how to explain it since i didnt really make sense(but i regret not givingher a reason now). so she replied with "oh. okay." i said felt really bad and she said "yeah" thats when i knew she was pissed. i asked if she was mad and that i was sorry. she said no that it was fine. i said okay and that we could have a sleepover sometime this week and she repliedwith a "yeah. maybe" so i said okay and asked her what she was up to. no reply. 7 hours later i said hey and still no reply. i know shes ignoring me. but what should i do. ive seen her get angry with other friends and this is exactly what she does. she ignores them when they text her but she still reads the text. so i dont know what to do. however this has happened to me multiple times (where my mom says do it another day) but she's never gotten this upset with me also somedays she's not able to hang out with me and i could have been mad at her those times as well. infact sometimes i have been but i just said that it was all right. I always felt you should forgive and forget but anyway i feel terrible about this whole dilemma and i dont know what else to say. please i need advice. im so upset. what should i say?