Happy Birthday, South!
No need to respond to her, but if you feel that you should, you can just write "Thanks!" and leave it at that.

Then go enjoy your day and try not to fixate on her and her message.

M: 43 H: 39
D: 14
Married 15 Together 16
BD: 6/2014
S: 8/2014
OW revealed 10/2014
Instigated dissolution 12/2014, in progress
So over it!