First of all, we got rid of the horrible old gas pibe mtb that she had been riding and got her a lighter weight mixte and put on a mtb crank with 38-26 chainrings to lower the gearing.
And when we're riding I carry most of the heavy stuff while she's carrying the lighter stuff in two small front panniers.
And recently we've started looking for a tandem - she's always wanted one and it's a great fitness equalizer. Plus it makes it so much easier to talk while riding. I realize that a tandem is not for everyone tho.