My tip would be to think more basic than phrases - instead of "Could you please repeat that?" try for something like "Once more, please?" or "Say it again, please?" It will be shorter, simpler and easier to remember, meaning she is more likely to use it.
Likewise a few simple phrases she can put nouns/verbs into are useful.
For example, food:
Do you have any....?
Pass the...please
Some more....please
I don't like....
With....please
Without....please
Things in the house:
Where is (the)...?
Is there a....? (Or you could stick to "do you have any/a")
Show me, please
Can you help me with....?
Language help:
Excuse me. I don't understand.
Slower, please?
Once again, please?
Don't overdo it because she'll never use any of them.
When I went on my French exchange I had one of those "gem" dictionaries so I could carry it around and so if I didn't know the word to go into the gap, I could look up single words at a time, that was really helpful. If she doesn't have one but she has a smartphone, the google translate app can be useful for the same thing - as long as she can trust herself not to over rely on it and use it to translate whole sentences at a time 
The key to languages is to start very small, very simple, think in terms of the language she knows being building blocks she can build what she wants to say/communicate from. Start there, rather than starting with the exact phrase in English you would use. That often leads to an overcomplicated translation.