Well … if you had more time, I would suggest exposure therapy using either a less aggressive or less obvious fairy-type such as flabébé or marill. However, seeing as time is of the essence, allow me to suggest this instead:
1. If at all possible, don’t see a horror movie. In fact, try to avoid any movie that would put you on edge. The calmer you’ll be after the movie, the easier the introduction will be.
2. Be honest with your date. Remember, a relationship is about trust and communication. If you share with your partner that you’re afraid of fairy-types but would still be open to meeting her clefable (not to speak for you, but the clefable is still part of your relationship), she may be understanding of your needs and either give you time or talk things through with you to come up with a strategy.
3. If she’s open to having you meet her clefable, remain calm during the encounter. You may wish to bring along your most trusted pokémon to have by your side. Additionally, consider using breathing exercises to ground yourself and keep your thoughts under control. Take the introduction slowly and communicate with your partner when you feel too uncomfortable to continue.
4. If at all possible, inform her of this fear before your date. This may seem awkward, but the sooner she knows about your condition, the sooner she’ll be able to help you—or the easier the introduction will be. She will, at the very least, have time to prepare on her side too.
Best of luck!