“She had stopped her own career; no one else did,” Ms. Lepera said in an interview. “For her to say, ‘Now I’m ready, so let’s hurry up’ — she could have been doing this all along.”

Ms. Lepera added that Dr. Luke has no choice but to follow through with his own lawsuit. “When someone who has so vigorously set out — consciously, clearly — to destroy someone’s reputation in the press is then backpedaling and refusing to prove those allegations in court, that signals a lack of credibility,” she said.

In his first public comments on the case since a string of tweets in February, Dr. Luke said he intended to take the defamation and breach of contract claims to trial, which could begin early next year.

“It’s been frustrating and painful for me and my family to have to endure false accusations and watch people rush to judgment,” Dr. Luke said in a statement. “Kesha has lost or dismissed her claims, and seems to want to erase what she started, without caring at all about the damage she has caused and continues to cause me, my businesses and my family.”

Dr. Luke’s highest-profile single this year, for Jennifer Lopez, was met with immediate backlash; a song crediting him has not reached the Top 10 this year.

In filings, Kesha’s lawyers have criticized Dr. Luke’s “scorched earth litigation tactics,” including additional defamation suits against the singer’s manager; her mother, Pebe Sebert; and a former lawyer, Mark Geragos.