Switching, for most of us, is about the energy we have with a partner, not about flipping a switch. So, if you push her dominant buttons then you really needn't worry about her switching roles on you (unless you're one of those rare folks that can push her submissive buttons as well, but it doesn't happen often).
You should also understand that she has two distinct sets of needs, and will probably need to have both met. That means multiple partners, usually, since it's rare to find one person you can switch with. If you can only fulfill her dominant needs, then it's likely that she'll need to have a dominant partner (or partners) as well. If you can't handle that, it's good to say so up front.
And, of course, like any other relationship (or potential relationship), if the chemistry/energy isn't there, it doesn't matter what percentage she defines herself as dominant, cuz it ain't gonna work regardless.
Fighting for peace is like fucking for virginity.