In the centre, try electric cinema, you can book a couch and get waiter service, I am sure there are some good films out and its such a novelty. Alternatively if she likes shopping you can go to the bullring (will be very busy), Selfridge's is cool for nice food, stationery bits and bobs and general browsing. The new library is nice too just to look around, you can get a great view from the top. Lunch in Brindley place or the cube or mailbox.