For me it has helped to have mental verbal cues, I basically sum up my floor routine in my head as I do it. However, I'm much older and everybody is different so I don't know it that helps your daughter. (Like, in my mind I'm going: turn, kick, prep and go, arm, arm, etc..)
One thing that helps some people with nerves is to think about 1 specific person they're performing for, as if they're only performing for that person and everybody else just happens to be there. But again, you'll have to find what works for her.
I also agree that the more you have it memorised super much, the more sure you are that you'll remember it under pressure. Just like how on an exam you may forget some stuff because of exam stress, but you'll usually remember your name etc. because that's second nature. A floor routine can become second nature too.
Finally, at this age it probably is also not a big issue. It's likely something she'll figure out with age and experience, and it's probably more common in her age group (Or if she started at a later age: it's probably more common among girls who are newer to competing.)