Thanks to your suggestions (I passed on the info) DD#1 found a chance to talk to waitstaff manager (WSM) about the possibility of setting up an interview. WSM said "Let me think about it. But in the mean time you need to work on your appearance."
I asked her if her uniform was clean and unwrinkled? How do you wear your hair? Do you look like you just crawled out of bed?
DD#1 said "No, it's nothing like that. WSM said that I need to smile more. She said that I always look a bit sad." They chatted for a few minutes so DD#1 was able to get some clarification from WSM.
So DD#1 and talked about that for a while. She said that she always puts a happy face on whenever she greets customers at the take-out window and especially when she takes phone orders. "You know, mom, when you're on the phone and put on a happy face the smile shows through your voice even when you're working with fussy customers. OldMgr taught me this. It works!"
It seems like the problem is when DD#1 is doing the by-rote tasks like filling the condiment containers or folding the pizza boxes WSM said "it sometimes looks like you're just not happy to be here."
DD#1 told me that when she's doing these tasks she's usually thinking about school stuff.
So, in the end, I think that DD#1 has a few positives on her side:
1. WSM said that she would think about it and didn't give DD#1 a definite no.
2. DD#1 learned about something that she needs improvement on and will work on this problem area.
3. WSM didn't ask her how long she planned on staying.
I appreciate everybody's input on this. I forgot to ask about personnel turnaround but this is a busy-trendy place so I do understand that only 6 months might not be in the best interest of the company to train a waitress.
We'll see what happens next.