In Audacity on Windows there are free plugins where you can adjust the stereo width in real-time, e.g.
In Audacity on Windows this can be done in one step using a free plugin where the equalization of mid & side can be adjusted separately in real-time … Graphic Equalizer Plugin, 7-Band, Harmonic [VST, AU, AAX] - Overtone GEQ - Voxengo
[ I would cut the treble on the side channel to reduce the sibilance ]