Written and first recorded by Steve Gibb (1978).
Hit version by Kenny Rogers (US #5/C&W #1/UK #42/CAN #8 1979).
From the wiki: “‘She Believes in Me’ was written by Steve Gibb (not the Steve Gibb, son of Barry Gibb) and is the tale of a songwriter who has a beloved, that while she supports him, he sometimes wonders why. The song first appeared on Gibb’s 1978 album Let Me Sing. Recorded by Kenny Rogers in 1979, it became one of his biggest crossover hits in the late spring of 1979, reaching #1 on the Billboard Country Singles chart and crossing over to the Top 5 of the Billboard Hot 100.”
Kenny Rogers, “She Believes in Me” (1979):