People get paid to write this garble.
It could be, "The falls, which are about fifty feet high, overlook Lake Tahoe."
It could be, "The falls, which is about fifty feet high, overlooks Lake Tahoe."
In the United States, we tend to treat "falls" as a plural and "waterfall" as a singular, but some of our brethren with their own versions of English write "falls is."
Sure, but the lady only had one fall.