Write a reply expressing your inability to attend the function.
2/R Dolly Apartments,
L.B. Akram Street,
Bijapur
8th October, 20_
Dear Radhika,
Thank you for your invitation to the wedding of your elder sister Roxana to be solemnized at Cusrow Baug on 11th November. I am glad that you remembered and invited me for the happy occasion. It has been extremely nice of you to invite me.
I wish I could participate in the function and witness it all personally, but I have not recovered completely from my recent illness. Doctors have advised complete rest for at least three weeks. You do not know how bad I am feeling to express my inability to attend your sister’s marriage.
My family joins me in conveying our best wishes to the newlyweds for a long, prosperous and happy married life.
Yours loving friend,
Gitanj ali