Not Pelosi necessarily but I've seen plenty of citations to the other lesser-ranked Democrats who came out in favor of impeachment much earlier than Pelosi. Maxine Waters, Rashida Tlaib, etc.
Which is accurate, as far as it goes, but does not prove that there existed a broad-based Democratic conspiracy to unseat Trump from the very beginning.
In theory, impeachment could have been pursued on Day 1 for emoluments clause violations. But, I don't think that would have been a smart, successful, or even Democratic strategy. Trump continuing to have a personal stake in his companies while in office is troubling but not necessarily impeachment-worthy without evidence of something more.
Personally I came out in favor of impeachment right about the same time as Pelosi: just a few months ago. And for me, it's all about the issues announced in the impeachment articles: the Ukraine call and obstruction. Not the much-hyped but overblown Mueller inquiry. Not family separations at the border, or betraying the Kurds, or anything else.