These statements led me to believe that.
To answer your question, no she won’t be eligible for ACA (aka Obamacare) on a temporary basis. This is what I had when I first came but we were already married and I had to show a bunch of stuff showing I’m eligible and it was a long term insurance; it also took several weeks to kick in.
Travel insurance doesn’t usually have good coverage (only emergencies) and from what I’ve been reading over the years here, K1s aren’t eligible because they’re not visiting, they actually relocate here to take up residence.
Waiting to marry (and consequently delaying filing AOS) puts a K1 holder in a vulnerable position, including both from an immigration perspective and the health insurance aspect. I never recommend waiting, especially if it’s to test your partner to see if they’ll bail because it’s too cold.