She'd be feeling pretty much all the emotions at once, which she probably can't handle.
Hopefully, she has some loyal staff who will keep her form doing anything stupid. Left to her own devices, she could do anything.
The smart move is: be a baroness. She doesn't really have a claim beyond that (she's not a legitimate heir so no claim to the crown) and she can't reveal her secret without weakening the only one inclined to do anything for her. Baroness ain't a bad gig, she can possibly marry up or otherwise combine her holdings to get even richer and if she can one day come to understand why her mother kept the secret she did she can live as happy a life as nobility allows.
But 14 year-olds aren't known for doing the smart thing.
Another option may be that because she's only 14 every year she could set aside the profit the barony makes her, depending on the number, training, weapons and armor of the troops in The Baronies Garrison the profit from her Barony could be anywhere from a mere 40 Gold a year up to almost 1,000 Gold a year
No matter how much profit the barony makes her per year the initial part of her plan is that she'd use most of the money she's made to buy land off owners that are desperate enough to sell and rent it out, maybe even renting to the former owners, she has a ambitious endgame plan but she knows, and freely admits, that she'll never live long enough to complete it
I will admit that depending on how much profit she makes per year in the early stages of her plan she could up buying land anywhere between every other year and every 10th year. Scary thought but its likely that it won't be as scary as it could be
Her plan is that overtime these extra earnings could amount to a few thousand Gold Coins a year more, and her eventual plan would be that whoever succeeds her will eventually be able to buy the title that's directly above hers and depending on the gender of her heir the title would be either Very Senior Baron or Very Senior Baroness
I will admit that even though the 14 year old Senior Baroness would love to live long enough that she could afford to be the 1 that pay's to have her families title upgraded to Very Senior Baroness she's realistic enough to know she won't live long enough