LindLLL

I'm applying for several PhD programs and master programs. My first school is due today in 10 minutes. Two of my professors have submitted their LOR a long time ago but this one professor still hasn't hers yet. I reminded her three days ago and she promised me that she will have it ready by today. But well. I'm so disappointed and sad. I know her and she knows me really well so I completely trusted her. I've been doing research with her for a while and she's also the head of the department so I believe she can really write me a strong LOR. I've already submitted my application and i hope that the school do accept late recommendation letters (if she's ever going to write it and submit it)... Did she just forget? just why? Should i find someone else to write? I know one other professor in person really well (since I'm from a liberal art college so we have a small faculty-student ratio) , but I've only taken one class with him, not sure if he has enough to write academically.