Good call on this... I'm terrible at picking out for my wife.
Does your significant other like shoes/flip flops? I can never go wrong with those and I bought her a pair of Rainbows last year that she absolutely loves:
https://www.amazon.com/s/ref=nb_sb_n...bow+flip+flops
This company is pretty cool too. If your shoes EVER wear out, just mail them back in for a replacement...