Mattel sold $53,000,000 of Princess Of Power toys in 1985, more than He-Man made in its first year. And that doesn't even count the sales of Horde toys, which were also supported by the She-Ra cartoon. There were a lot of girls watching He-Man, which was the rationale for the spin-off.
She-Ra and He-Man ran concurrently for a good sixty episodes in 1985 and then in 1986 She-Ra ran for an extra half-a-season after He-Man was axed.
No, she/it wasn't.