You can try to make your budgie's cage more appealing, add some new toys to keep her occupied. At first you can spend some time with her by sitting close to the cage while she is inside and encourage her to play with one of the toys she has in the cage.
By doing this, you will be showing her the cage is a fun place to be in and soon she will realize this and will be able to occupy herself in her safe place, while you are busy working and can't devote your full attention to her or even when you need to go out.
It's very important not only for budgies but also our pet birds in general to feel comfortable in their cages and to be occupied during the time they can't be let out of the cages for flight time.
You may want to schedule the time your budgie has for out of cage time. If you set a routine for her, she will soon get used to it and respond very well.
I've learnt with my pets that they like routine and they know the exact time I come to get them for their out of cage play time. They expect it and like the predictability of a scheduled routine.
RIP sweet Tito (Summer 2008 - January 17th 2013).
You are missed and never will be forgotten.