You shouldn't be worried about the number close.
As long as you use the other 9 questions to your advantage, you should be able to have build up enough comfort to get a number without a problem.
Try not to make it so formal also. Don't be like
Question 1: blah
girl answers
Question : blah blah
...
Dwell on her answer. Keep the conversations going. Each "Interview" will take longer, but it will bee much more beneficial for you to do it like that.
Then, at the end, say something like "Well, I promised only 10 questions, and this last one isn't THAT important so you can just give me your number instead.

"
Now as for questions,
"Am I too good looking to be a film director, and why?"
"Am I too cool to be a film director, and why?"
or something along those lines.
If she says "No" to those, cut her off with "Ok, interview's over." and just leave it at that.
If she is like "Uhh...." or "I don't know..." or "I don't know you that well..." cut her off with "Please stay on topic. Time is money, especially in production

"
.......there's my 2cents