She happens to possess magic, which allows her to fly (only when her wings are present; she can poof them away and make them reappear whenever) and most of the time video game logic is applied to her. This allows her to have an inventory she can stash things in and fetch things out of (limited to 16 items), and when she dies for any reason she can respawn later at her castle.
Most of her magic though is related to transformations, and she has control over her form to some extent (such as to change size or to become a Pachirisu temporarily for access to electricity) and her milk can have transformation magic put in it.
She was a regular feral squirrel in Ft.Wayne who happened to be around for a serious accident in a toaster factory and that turned her neon green and an anthropomorphic squirrel, aged about 16 or so. This also created the Animal Crossing town Ft.Toast and the kingdom of Toasterland in the Chatverse, the two of which she was destined to rule, though she was unaware of it at the time, also unaware that she was in fact an Animal Crossing squirrel rather than a regular anthro. She lived at the toaster factory for awhile and the workers were very nice to her and she had a lot of Doritos available to eat.
While there, she heard of a legend involving four high school students whose name started with J, and one had gone missing, named Jon. However, through a lot of convoluted logic that only Nova could come up with she determined that Jon knew the location of an item of extraordinary power, and that she needed to find magic Dorito in order to find Jon. She got a building constructed for a group she named the Society of Doritos and called together tons of people she knew as well as The Gentlemanne's Exploratory Guild to join the society.
She held a meeting that explained what the group was about and what they had to find, and Dorito-hater Wyatt Williams formed the Pringles Legion to fight against the Doritos Society (though it was primarily in the form of pranks back and forth) and their goal was initially to find the Pringles mascot, even though he actually was among the members and Wyatt didn't know. (The Pringles mascot had a monopoly on the tube can potato chip market, made a fortune, then took over Parker Brothers and grew older and became the Monopoly guy).
There was another group named the Scheme Team that mostly created chaos by "Scheming" against people and the Pringles Legion decided to make use of it to bother the Doritos Society, and the first thing they did was take over Taco Bell on the day they knew Nova was going to enter with the Society and use a "buy 1 get 127 free" coupon on tacos, and they replaced the taco shells with Dorito chip material and the combined amount of deliciousness of all 128 tacos was so great that it caused a change in physics, so that if you were traveling at the EXACT speed in a certain physics problem about a motorcycle (The Speid of Reid, about 12.27 meters/second or 27 miles per hour) you could teleport to any other universe.
This was discovered by Bill Nye when the Billy Alliance (Nye, Gates, Mays) had allied with the Doritos Society and the war between Doritos and Pringles went to more and more extreme levels, and the malicious and mysterious EQOW (EarthQuaker Oats Warriors) group headed by Wahovipab discovered the change and came from Badverse to this one to find the magic Dorito. They were a group dedicated to promoting oatmeal and they disapproved of chips and wanted to use the mysterious item of extraordinary power to get rid of all Doritos and Pringles and force people to eat oatmeal instead, and the lack of Doritos would destroy the world with earthquakes.
The Doritos Society and Pringles Legion reluctantly joined forces for the duration of the new battle to form the Chip Alliance and they would wage war against the EQOW. Eventually the Chip Alliance would prevail and the EQOW would surrender just after it found out the location of the magic Dorito, and it would hand over that information. The magic Dorito would be found and Jon was located, the item being the magical and powerful Scepter of Awesome which was then found after that, which was deemed too dangerous to keep around because of how powerful it was.
At this point, Isabelle from Animal Crossing had finally caught up with Nova after looking all over the place for her, and explained that she was, in fact, an Animal Crossing squirrel and explained everything about Toasterland and what the toaster factory incident did and that Ft.Toast and Toasterland needed a princess to run it. It was decided the safest thing to do with the scepter would be for Nova to take it to the Chatverse with her and keep it safe in Toasterland, where she now rules as its princess. Toasterland also existed in the Wyatt World universe somehow in Europe's place after the original countries crumbled.