Complex sentence: Mette was politically active as her husband's advisor, and thereby became a target for slander and rumors; she was, among other things, rumored to have taken part in plots to murder Sten Sture the Elder.
Split into simpler sentences: Mette was politically active as her husband's advisor, and thereby became a target for slander and rumors. She was, among other things, rumored to have taken part in plots to murder Sten Sture the Elder.