What will she do during the next session?
I think an important factor, her character is dead, if your answer is: “waiting for party to discover resurrection is impossible and proceed to make a new character on the spot.” I doubt it'll be fun for her; even for a Ravenlofty campaign, that's still too much. Just tell her and save everyone some time.
But you can let her revive the character, with a twist.
See, Curse of Strahd has its origin in the old "Domain of Dread" Ravenloft setting, which has a lot of interesting twists. There is an adventure league document on this particular instance, letting the dark powers of Ravenloft resurrect her:
Second, the player can choose to have the Dark Powers of Ravenloft resurrect the character for free. If the player chooses resurrection, the character returns to play at the start of the next round with full hit points and spells. However, this dark resurrection leaves the character tainted by shadow.
You can check out the full document here.
But I believe you should still get consent from the player first, just personal preference. Remember everyone's here to have fun; fun's had, mission accomplished.
Also something to remember: tension is good. Taking away the fear of death takes away from the tension, doubly bad for a Gothic horror setting. Absolutely DO NOT resurrect her without penalty; even if said penalty is a cosmetic "taint", players will fill in the blanks and think it's something terrible.