Mad, Sad and confused

Guys...I dont understand...one of my absolute best friends is being really grumpy with me...and I think she hates me...and I dont know why...I dont know what I did to make her mad...all her msn names seem so happy...but when I talk to her...she gets mad and AGH...I hate this! I feel like Im losing her...and I dont want too...shes sooo cool...and shes just...awesome. I left my house one time super early to go and spend time with her before a wedding...and now she hates me? What the Heck?!?!?! I try and be a good friend...and she shoves me away...why?!?