Hello Hans,
Thanks for stopping in with your question. It's great to hear you're making your Walt Disney World Resort vacation plans.
I know you mention that you can't locate your Resort reservation confirmation email. What I don't know is whether or not you might have
linked your reservation to your My Disney Account at some point. In the chance that you did link your reservation to your My Disney Experience account, you might be able to make the modifications through your "My Plans" area if you see
a link for modifications next to your Resort hotel reservation.
You can always contact the Walt Disney World Resort at (407) 934-7639 and speak with a Cast Member about making the modifications to add your daughter to your reservation.
If your daughter typically makes most of your Walt Disney World Resort plans, then she is probably very familiar with the
My Disney Experience mobile app. It's such a convenient app for making and managing all your plans for your Walt Disney World Resort stay.
Your daughter will also want to be sure to make theme park reservations through the
Disney Park Pass system if your plans include playing in the theme parks.
You and your daughter can come back at any time to ask questions here at planDisney if you're looking for suggestions on how to make the most of your magical stay.
Here's wishing you lots of fun for your Walt Disney World Resort trip!
Jerry