PARIS — Marianne Faithfull is in higher spirits than you might think. “On the whole, I’ve been pretty happy for years,” Faithfull muses over a glass of Coke Zero at the trendy Hôtel Costes in Paris.

Faithfull was a pop star, part of British rock royalty. The lows began with her use of narcotics and ended with time spent as a homeless junkie.