Totally agree that learning to "lose" gracefully is equally important as learning to "win" gracefully. I can't stand to see a girl sulking when they don't place as high as they wanted because there are usually a ton of girls without medals that would do anything to be up there getting that medal.
I tell my daughter that the person that "wins" the meet just means that on THAT day, they gave the best performance overall, it doesn't mean they are the BEST gymnast forever. I think it has helped her to not think that it is attainable for her and also the few times she HAS actually placed 1st in AA or an event, keeps her from letting it go to her head. Being at different kinds of meets is part of this sport. DDs team goes to some really big invitationals, where competition is usually really tough and also some smaller meets where competition is usually more equal.
I never focus on scores with my daughter as goals OR as indicators of improvement. She has already learned that judging is very subjective and one meet she can actually do better and get a lower score and vice versa. Usually on the day before the meet, we talk about her previous meet and she makes some goals for the meet (usually little things, stay on beam, bigger leap, hold handstand longer, things she has been working on in practice, etc.).
Since she is young (I assume DD5 means she is 5?), you might want to talk about how every meet is different and that how you place or score isn't what is important, that doing your best and hopefully setting some goals and making them is. Might be a good time to start a fun after meet tradition (like getting an Icee at Circle K or an ice cream cone from somewhere) that makes it so you are always celebrating, regardless of how the meet went. Just getting out there in front of judges and a ton of people and doing your routines is an accomplishment!
Hope she has fun at the big meet!