What does she do that is most "her"? You know? The thing she does that makes you doubt your GT denial the most because you just can't believe that other kids do that thing?
Film that.
Often it involves getting a child to talk about what they're passionate about, especially if they drew or wrote something to go with what they're saying. Creative spelling doesn't really matter if you have video of her reading/explaining what she wrote.
Turning the camera on casually and setting it on the table without letting her know that it's on is a good idea if she's reluctant to be herself with it on.
BTW, I don't think that 1st grade work would get a 5yo into DYS. I could be wrong, but that's my impression. I'd recommend that you show her doing late 2nd grade work at least, and 3rd would be better. Remember that you're not merely trying to show that she's GT, you're trying to show that she's PG. The usual rec is at least 3 years ahead of age level, and 3+ is more persuasive.
HTH!
