But she has offered to implement her ideas herself. So let her. If she is wrong, her lack of capability will be revealed. However, if she is right, management looks like morons.
This argument is just lame. When a company pays you a salary, you work for them. So "offering to implement her ideas" is almost like "offering to work during office hours". Worse, it's "offering to do something really risky instead of your assigned task during office hours".
If she is wrong, of course her lack of capability will be revealed -- but will she be able to fix the mess if it goes wrong? What about the cost of the mistake?