Question

あ

マーカー部分の構文を解説して欲しいです。(特にbut周辺)

加えての質問で
Laufer vigorously deniedは分詞構文か関係代名詞節(thatの省略)どちらで考えても良いですか？

The case, which involves a small hotel in Maine, could weaken ADA protections and have broader
ramifications* for the enforcement of other civil rights laws, legal experts say.
It was made somewhat more complicated this summer, when Laufer's former attorney in Maryland
hotel lawsuits was disciplined for improper conduct. After a court order, lawyers for the Maine hotel
accused Laufer of participating in "unethical extortionate* scheme" - an allegation* Laufer
vigorously denies, but (4) one that led in part to her request that the high court dismiss her case.
(オ)
an