Settings > Options > find the tab for Display > Click + on Client Information > Click Spouse First Name > Click the > to add Spouse First Name to the list on the right > Highlight Spouse First Name to move it to the top of the list by clicking Up > Click OK

Now your Clients tab will show the Spouse First Name in the left most column and they will be sorted alphabetically. Type melissa and VOILA! Thar she be!

FYI - to change what is in the left column, just click the desired column and drag it to that position.