Originally Posted by
bmw303
if your spouse doesn't have elite status with united or an E+ subscription, then you have to purchase it for each flight. When you select a blue E+ seat, you'll see the price.
Clarifying my original post for OP
If you're flying with your spouse but you're on a separate ticket, United will put her next to you in E+ (assuming you are Gold or above, or Silver within 24 hours of departure). You have to call in.
If you're flying with your spouse on the same ticket, you should have no problem selecting an E+ seat for both assuming you are Gold or above, or Silver within 24 hours of departure.
If your spouse is Premier Gold or above (or silver within 24 hours of departure or E+ subscriber), then the seats should be free. Call if its not.
If you're not flying with your spouse, and if your spouse is not a Premier Gold or above (or silver within 24 hours or E+ subscriber) then your spouse is not eligible for complimentary E+. Then you have to purchase. Doesn't matter if you are an elite using your miles.