I should’ve said the House, not just Pelosi. The House has denied seats on more than one occasion, but perhaps you just mean under this Congress?
I know you’re referring to the rules of each house as to seating in the Constitution, but I believe the one SCOTUS precedent actually forced the House to admit Adam Clayton Powell. I can’t remember all of the reasoning. I think the Court said the governance of the house granted by the Constitution was not a plenary power that could be exercised in defiance of the will of the electorate. Burris actually cited the precedent when he threatened Senate Dems with a lawsuit earlier in this Congress.