I don't know about QF specifically but generally part-time positions are very sought after and not many are offered. It can take several years to get a part-time position. They do not recruitment for part-time directly, you have to start full-time and then go on a wait list.
If you are a working mum it might be better for you to apply to Jetstar because they only do day trips and that will solve part of the problem for you. You might also want to consider a casual position as then you may get less hours than a full-time load during certain times of the year.
Sorry I can't give you better news, but these are the facts all working mums in aviation have to face.