Despite what the polls may say, Cheney siphons off Trump votes, not Biden votes. Ask yourself if you know any Biden voter who would pick Cheney instead of Biden. It’s simply not a crossover anyone would make. The reverse is clearly not true of Trump voters, many of whom were Republicans who held their nose and voted for him because he was the Republican on the ballot. If a competing Republican that more closely matches their ideology is available even if she is an independent they will pick her instead.