I think I figured out a solution that I think will make Itzel and me happy. I have to take the next part of my exam the first week of September. Most likely, I will be going home to California to take it there, since I am familiar with that testing center. And if the breeder does have a puppy for me that is born in June or a little later, she will most likely be coming home to me in September/ October. So my plan is to take Itzel with me to NY in September instead of June. I believe someone had mentioned that as an option. This way, I will be settled in and she won't be alone for too long before her little sister comes along.
Thank you so much for all of your advice, everyone. I truly appreciate it. I feel like a huge weight has been lifted.
With this solution, I think Itzel and I can both be really happy.