I'm not politically minded so I'm confused as to how you're interpreting that.
She didn't say that if the FDA didn't approve it and Trump somehow magically bypassed the process and put it out there for people to take that she wouldn't take it. She implied that if the FDA approved it and Trump said people should take it that she wouldn't.
Debates are debates and people say stupid things, but that was far from the only moment of vaccine hesitancy to happen on the left just because Trump was president. Now, of course, it's flipped - and both show just how tribal America has become.
Harris's answer was the right one, and the same one I would have given. An unqualified "yes" would be saying you'd take a vaccine approved by the administration even if the medical community wasn't confident in it, and the phrasing of the question was designed to elicit that clarification.
And let's not pretend it's surprising that her qualification was even needed; We're talking about the same president who used the presidential soap box to urge people to try curing and preventing COVID using Hydroxychloroquine despite no such recommendation from health officials or the medical community at large.
"But if Donald Trump tells us we should take it, I'm not taking it." -Kamala Harris
Let’s not act like both parties don’t do the exact same thing, eh?