I agree that you need to find out exactly what the problem is. How can you fix it if you don't know what it is? Sometimes we women expect you to read our minds...I know, it's completely unfair. I also know first hand that being a stay at home mom is not an easy job. I (obviously) don't know you, or your reactions to things, so if I'm off, just ignore me
But sometimes when I've had a hard or just plain long day with the kids, I'm in a cruddy mood, but don't want to vent to my husband because I know he's had a long day too. Sometimes I feel guilty that he's the one with a job (that he's not really fond of) and that even though we agreed that I'd stay home, I feel guilty if I complain because I'm not bringing in any money and he has to work long, frustrating hours every day. Maybe for some reason, she's afraid of your reaction if she tells you she's just had a crappy day and needs to stew about it. Sometimes husbands forget that we wives get our "knickers in a knot" too and can't be happy-go-lucky all the time. Just some thoughts. I hope things work out for you!