The best way to potty train her would be to crate her. Find the smallest crate you can, and if it's still too big, stuff towels or something in the back. She should only have room to stand up, turn around, and lay down. Put her into her crate at night, and when you're not home to supervise her. Make sure you're taking her out to potty first thing in the morning, after eating/drinking, and after heavy playtime. Also probably about every hour in between all of those things. The key to potty training is prevention. Potty training will be tough but the time you put into it will be worth it in the end.
Purina Puppy Chow is not a very good food. If you do some searching in the Health and Diet forum, you'll find some wonderful foods that many here recommend. I would switch, but not immediately. Give her a week or two to settle in before you upset her tummy.
For treats, we use Cheerios, and little bits of cheese. Yorkie Yummies are also fantastic but your little one will be too small to chew those. I have no idea about the cottage cheese, maybe someone else will come along and help.
Congrats on your new bundle of joy and welcome to YT!
