a) Republicans get their nominee confirmed. Dems don't bother fighting it because they ultimately don't have the votes to stop her anyway.
b) Republicans get their nominee confirmed. Senators face unprecedented deluge of angry constituents. The nominee's reputation is publicly dragged through the mud. Two R senators forced to break with their party. Left-leaning people all over the country learned their representatives' phone numbers and have gotten into the habit of calling every day. D senators are united and pledge to keep fighting Trump's appointees because their constituents demand it.
Sure, they get DeVos either way, but which do you think the GOP would have preferred?
Why should we make this easier for them just because?