You said she got moved away from the busier part of the house because of the cat?
I'm thinking get her back to the main part of the house and train the cat!
Water in a spray bottle does wonder to get the message across. As long as you make sure that the cage is in a place that the cat can't get to and push around (a big hook firmly screwed to the ceiling if nowhere else is available). At first have the bird in the busier part of the house only when you"re around. As soon as and every time the cat shows any sort of interest in the bird (looking at it is interest) say 'NO' in your biggest voice at the same time as you reward him with a squirt of water. Keep doing this as long as he keeps showing interest -he'll stop sooner than you think. Then the only thing you have to do is keep the spray bottle in full sight of the cat near the cage, at all times. A little reminder every so often will make sure that your cat keeps ignoring the bird.
As a mother, I know that when I say 'we can't afford it' I also think 'but see if you can earn it.' Is there any way you could make a deal with your mom so that either of you can buy a second bird?
In any case, she is a flock bird and needs company, from you as well as the rest of the family if at all possible. When there is no-one else in the house keep putting music on or even better, budgies sounds (some nice long tracks on YouTube).
Toys can be bought but they can also be made. Check out the DIY section on the forum.
All the best!