Giving Away Of Bride

I am having my daughter walk me down the aisle. She is 21, and my B/F`s daughter will stand with him (in place of a best man) and she is 26.
I was simply going to list them as daughter of the Bride and Groom on the program. Since I could not find an appropriate term for my B/F`s daughter`s fuinction.I am not quite sure if esscort would be correct in her case.
I think since your son is younger I would go with something like "special esscort" since it is very special to have him do this in your wedding.