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Вы чертовски умны but вы чертовски умный.

I just realized that I fucked up a little bit. No, not the future form, but just present.

Just conjugate all the other words in conjunction with plural вы.

Вы очень красивы:good: Вы очень красива:wife:

It's not that genitive requires ни, no. It's just when you have consecutive negations those не turn to ни and act as conjunctions, rather than particles.

Я не знаю ни тебя, ни его.
Он не умел ни...

I'd personally say:

Спасибо за то, что ты появилась в моей жизни.

I don't know... вошла? Doesn't sound that elegant to me. Maybe it's just me anyway.