Hi & welcome to YT
My boy had oily hair whe he was a puppy. I think that it's a pretty common thing. He eventually outgrew it. But even now, if I wait longer than a week to give him a bath, he'll start to get oily. Someone recommended that I try Sebamed shampoo & it actually did help. Here's a link:
sebamedusa.com I had never heard of it before, but it's about $13 & they have it at a lot of pharmacies near me. They also have a conditioner. If she gets REALLY oily, you might want to check with your vet. But I've seen the oily head issue come up here more than a few times. My old groomer also used to tell me about all of his "greasy Yorkies" clients. So you're not alone
Your little girl is a cutie pie! Good luck!