That's a trope I see getting used a lot, but the specifics can really make or break the story. From the novels I've read, her abilities usually follow a pattern tied to lineage, but with a twist because of the 'secret' part. She's often a genetic anomaly, inheriting more from her father's royal Lycan line than anyone expected, but with it suppressed or manifesting in weird ways until a catalyst event.
Common ones are an alpha command voice that works on other species, not just werewolves, which creates interesting political drama. There's also the potential for a pure silver immunity that flips the traditional weakness on its head, making her a terrifying wildcard in conflicts. I've noticed a trend toward her having a healing factor that works on others, a sort of empathic regeneration that marks her as a natural leader or a living treasure to be controlled.
Beyond the physical, a lot of authors give her a psychic or emotional 'pack sense' that extends beyond her father's territory, letting her feel the health of the entire Lycan nation, which is a huge burden. The best execution I've seen was in 'The Alpha's Unseen Heir,' where her hidden ability was actually a calming aura that could stop a rampage, making her less of a weapon and more of a necessary balance to the king's fury. It gave the story more depth than just another power fantasy.
Sometimes, the 'hidden' part is that she appears human for years, and the ability is a latent potential to ascend to a higher form of Lycan, like a Dire or an Ancient, which of course every faction wants to exploit for their own ends.