Pam - If DD wants to try to test again, I would let her try, however, I would *try* to explain to her that if she doesn't get into G/T, she can do her best to excel at the level she is in.
It's hard for me to watch my DD have to work so hard to make honor roll (which she does, but its 'painful') when everything about school came so naturally for me. I never cracked a book, was in all accellerated classes (we didn't have a true g/t program then), and got nothing but A's through high school. Sometimes its hard for me to remember that her brain doesn't work like mine... (and I have a Master's degree in education... I *should* be more sympathetic to her).
My DS on the other hand, takes after me- I'm glad that he's younger, so that she doesn't feel the need to 'be like him'.
If I were you, I would also make sure that she understands that if she DOES go into the G/T program, and she is struggling, she needs to let you know. Kids tend to be very proud and not ask for the help they need, thinking that it will make them look like a failure.
Just my two cents...