Hacer un feo a alguien

Hacer un feo a alguien
 

Usado en contextos como refutar una invitacion de comida, fiesta, boda etcc.
English?

to tender back regrets

Ej:
Voy a ir a la boda de su hija, por no hacerla un feo, pero deberia no ir, no se porta bien con su hermano.
CAn u translate this using the expression ? I isolation I don't grasp it.

to snub

Here is my try, (with 3 options!) :)

I am going [to go] to their daughter's wedding, just not to snub/slight her, [or not to be rude with her] but I shouldn't go, as she treats her brother badly.

y que es eso de tender back regrets

To tender = ofrecer, presentar
regrets = excusas
5. regrets, a polite, usually formal refusal of an invitation: I sent her my regrets.

As far as "back" is concerned, I am not totally sure, but I take Poli will illuminate us...
Something on the order of "echarse atrás"?
"Presentar mis excusas echándome atrás"?
"O lamentar tener que echarse atrás"?
Por ahí deben ir los tiros...

Now that I think of it to tender regrets is better than to tender back regrets.(to send back /to sent)
When one receives a formal invitation with an RSVP, if you can't go, it
is polite tender your regrets.

Ok, I see now. Thanks.