Dear Maria,
I'm writing this e-mail to apologise for not attending to our meeting, but I've been very busy with my exams. On Monday a have a very difficult exam, so I can't meet you on Sunday, I'm very sorry about it. If you like we still can go to the cinema the next weekend, and we can watch black swan, beacause everybody who have seen it have told me that it's a really good film. If you don't want I can understand it, but I really want to see you soon, because it's been too long since we saw eachother and I have a lot of things to tell you. I hope you don't mind too much and if you can meet next week just call me!
Take care, Sara