Hi mbrocks,
Your problem is not unique. As is so common with family, we tend to be less diplomatic with the ones we love, which can cause much more strife in a dance partnership than in one where the two people are just dance partners. Not so say that people who only dance together don't go at it pretty fiercely sometimes too, but never mind that for now.
I teach a married couple. They have come a very long way and are now dancing at a very high level in the open smooth. I'll tell you what my partner and I have done with them in the hopes that some of this can apply to you.
1) Always try to figure out what you may have done incorrectly rather than assume that it was your partner's fault. When you have a moment that isn't working or feeling good, both parties need to step back and make sure that they are doing their respective jobs correctly. The odds are, you both could have done something better and made the other person's job easier.
2) If it becomes clear that the other person is the one messing up, ask them what you can do to make their correction easier. That way you can figure out your part more accurately (either how to clarify your lead or how to more accurately respond as a follow), and you create a situation where it becomes less about who is right and who is wrong and more about how you work together to get it right.
3) If you cannot figure out what the problem is, make a note of what the issue is, and take it to a teacher to have them help you sort it out. Don't wait until you are both irritated with each other to stop. As soon as you see that between the two of you you do not have enough information or understanding to fix the problem yourselves, drop it and move on to something else. Don't ruin your practice session over some-- in the grand scheme of things -- completely unimportant moment.
My partner and I adhere to these rules, and in 7 years of dancing together, we have never had a fight. We have not always agreed on things, but we have been able to either fix the problem, or know when to just let it go. Granted, we are not married, but we have imparted this philosophy on our married couple, and they have managed to temper their fighting as well. Remember that your number one job as a dance partner is to create a safe learning environment for your partner. You have to be each other's number one fan and helper. If you both do this, you may find that you can teach each other quite a bit and even find that your ability to communicate with one another improves greatly both on and off the floor.
I hope that this does not come off as being terribly corny, but I very seriously believe in approaching your dancing in this way, whether or not you are married to your partner. I hope you find this helpful and that you and your wife end up loving your time together on the floor.
Lorena