I found a wavy line much easier to manage when I first started quilting. You probably could do it without a walking foot, but it would be soooo much easier with one. I also would purchase a name brand one for your machine. There are generic ones out there, but they are usually much flimsier than the one made by a sewing machine company. Spendy, but worth it.
I think your auntie should buy it for you as it's her fault you need one!