Hi,
Uncle will give u advice.
First of all, don't ask her numbers point blank just like that.
She's on the job working and u will come as a harassment, or as a
weirdo possibly. It will not work out positively.
What u can do, since it's not so convinient to strike a chat with
her there, well, u can wait until her shift is over and approach
her then.
When u approach her, don't start asking for her numbers
immidiately. That's not too good. You will come off too
strongly.
Start a casual chat first, then depending on whether u think you
can get her numbers or not, u can either: leave it as it is and
then chat with her again next time (repeat a few times), or, if you
are both finally relaxed and seem to click, u can casually mention
something about the weekend or the new ballet show. Tell her you
coincidentally have extra tickets. Then ask her whether she wants
to come to see the show. If she seems interested, suggest to her
maybe you two can go together. Then ask for her contacts. Either to
confirm, to tell more details, or something like that. Now u have
her numbers as well as a date.
Like this ok.
I really don't think if u ask her numbers point blank, without any
chatting sessions first, and worse, while she's working, will be
successful. Don't do that ok. She will probably make a mental note
to remember to avoid u.