I would recommend maintaining the idea that she can't curse Strahd. Giving him vulnerability to the party's favorite damage type can kill Strahd in a huge hurry...at the very least, she can eat one of his Legendary Resistances. ([https://www.reddit.com/r/CurseofStrahd/comments/8wct9k/my_notes_on_ezmerelda_davenir_vistani_monster/ Source])

Ezmerelda is a veteran monster hunter who was trained by the legendary monster hunter, Rudolph van Richten. As a result, she is really, really good at killing monsters. ([https://www.reddit.com/r/CurseofStrahd/comments/8wct9k/my_notes_on_ezmerelda_davenir_vistani_monster/ Source])

Ezmerelda is a veteran monster hunter who was trained by the legendary monster hunter, [[Rudolph van Richten]]. As a result, she is really, really good at killing monsters. (After all, in this module van Richten is only CR 5...the same as a Vampire Spawn, but he has canonically soloed mature vampires (CR13).) Ezmerelda will often quote from the Van Richten's Guides from AD&D2E, providing both anecdotes and useful information. ([https://www.reddit.com/r/CurseofStrahd/comments/8wct9k/my_notes_on_ezmerelda_davenir_vistani_monster/ Source])

Finding a monster that Ezmerelda doesn't know anything about should be spectacularly rare. As a rule, she'll know what she's fighting, what to expect from that enemy, how it is likely to fight you, and how to best kill it. If fighting with a party, she'll share that info. ([https://www.reddit.com/r/CurseofStrahd/comments/8wct9k/my_notes_on_ezmerelda_davenir_vistani_monster/ Source])

Will do her best to drill 'vital information' into allies' heads. ([https://www.reddit.com/r/CurseofStrahd/comments/8wct9k/my_notes_on_ezmerelda_davenir_vistani_monster/ Source])