Re: So, we're now over legally.. Question.
OP, I suggest you send a registered return receipt letter notifying her about tax filing, and that you will file as married filing separately. Keep it to that, other than any information needed to each properly file your tax returns. I'd also suggest that you file it ASAP (before she can) with any items that might be in contention, so she can't file using the same items (assuming there are any).
If you have more to say to her, keep it separate from business.
Love is an ideal thing; marriage is a real thing; a confusion of the real with the ideal never goes unpunished. - Johann Wolfgang von Goethe
CELIBACY IS NOT HEREDITARY.