n. The practice of one woman trying to do better than or to prove herself superior to another woman.
2002
Russia had already had a female cosmonaut, Valentina Tereshkova, in orbit in 1963 and, in a further show of one-up-womanship, had a second, Svetlana Savitskaya, seven months before Ride.
1977 (earliest)
"My Old Lady" is a tour de force of feminist one-upwomanship.
This word is an obvious play on one-upmanship, which was first recorded in 1952. It's so obvious, in fact, that I'm sure its first usage must have appeared not long after one-upmanship's debut. Still, the earliest citation I could find is only from 1977.