Hey Howdy Hey Christina and welcome to planDisney!
Bay Lake Tower at Disney's Contemporary Resort is amazing for so many reasons. Not only is the resort itself immaculate, but the amenities of food offerings, the pools and transportation to a couple of the parks make this one of the top resorts to visit. Don't even get me started on the views of the fireworks in Magic Kingdom! Before I get too lost in this amazing resort, let's talk about your room situation with your aunt.
Christina, as the Cast Members you spoke with mentioned, your aunt is more than welcome to visit for a night. There may be a cost associated with her staying the night depending on how many are currently booked for your room. Disney typically allows 2 adults to stay in one room before an added fee is associated with 3 or more. In Disney Deluxe Resorts, this nightly charge is typically $35.00 with prices subject to change without notice. Once you check her in at the front desk you should be all set!
While everyone knows how great the fireworks in Magic Kingdom can be viewed from California Grill at the top of the Contemporary, there are also a few other areas you might want to check out. The observation deck on level 3 of the resort is a great place to view the fireworks. You can also catch the walkway from the Contemporary to Bay Lake as another great place to catch a view. One special memory I have is our first time staying there as a family and my youngest fell asleep in the room but I was able to sneak out with my older 2 and watch from the elevator area which has a lot of viewing on each floor with the higher you go the better the view! All in all, you will have a spectacular view of the fireworks no matter where you are.
I hope you have a Magical time on your upcoming vacation and please let us know if you have any other questions!
To Infinity and Beyond,
Nick