Pelosi at the most is an socially inept elderly lady from San Francisco. The GOP absolutely HATES her because she is an extremely effective political opponent. She literally out performed a sitting president (Obama) in terms of fundraising, which is a feat.
How to chip away at her? Convince your base she's a nut job. Make it look like the Dem house is running around with their head cut off. It would be akin to Dem's casting McConnell as a loon because he's an effective Senate leader (though the cracks in his expertise are starting to show in the trainwreck known as the AHCA.)
The best they have is out of context quotes like "we have to pass the bill to see what's in it."
The most advantageous thing the Dems could do is hoist a figurehead to the speaker position, but never actually remove her. Hate against her is driven mostly from being what I mentioned, an elderly woman from super liberal San Francisco. Putting someone like a white male from the Midwest in as leadership but have Pelosi run the strings from behind might be the only thing they might want to do.
That being said, the GOP will bring extremely mundane details and out of context quotes from the NEXT speaker and use that as a decade long smear campaign as per usual.