A good question.. marginally taller I think, but not so much that I felt I had to transfer her to a flat base.
However.. particularly as I dont recall Romana 2 as being especially tall.. she's fine next to the tall 4th Doctor figure, which of course is where you're going to find her. And I feel she needs the slotta base still.
So Id say a tad taller than some earlier figures, but not in the same league as the 4th Doctor.
My Black Tree Leela and Romana are in the bin, and I hope CD will keep on causing me to do the same to some more. Im fine with their aliens and monsters but they were never quite as good with the human characters. And it was a long time ago.