Dear Mary, 

I'm very sorry for what I've done。I am very sorry that I can not take part in your party . It is pity to me because of my emercy thing need to be dealt with . I hope you will have one good time for the party . I really love you ! Please give my regards to our friends !If possible ,please do not forget to inform me if you have the party next time . I shall come to it on time. If I could do something for your party ,please feel free to contact me . That would be my pleasure. Above all , I apologize again for my absence from the party ! Good luck to you all ! 

Yours truly, Ellen