We had this issue with our Dd6 when she 3-4, I would come home from deployment and she would only listen to me. While I was gone she would do what ever Dw would say, but as soon as I stepped foot back into the house, words coming out of Dw's mouth meant nothing. We fixed it through having me explain to her she needs to listen, and a mix of time outs. I would talk to your SO about it, and then have him talk to her and try to explain it as best as possible that she has to listen to both of you. It took us a month, but it worked and she hasn't had any relapses so far.

Or you could go all Lion on her.

EXACT same thing going on in my house @FoulMouthedSailor! DH deployed, now all of a sudden, I am the primary disciplinarian. DD is getting used to listening to me, begrudgingly, but I know that as soon as DH comes back, my words are null and void again! With him, he says it ONCE, in a nice, calm voice, and its DONE--no problem. Me? Why must I repeat my requests a million times, finally resulting in SCREAMING and yanking my hair out, before DD even considers listening? I agree with @skatermom as well! Recently, sending dd to her room for a few minutes to "cool down" after squealing at me for asking her to please not throw the tennis ball in the house (HOW DARE I?) has worked. Also, before he left, DH told DD to listen to everything Mommy says. I tend to remind her of that every few hours or so, as needed. Since she wants to make Daddy happy, I say "Daddy told you to listen to Mommy. Guess I'll have to call him and tell him your aren't listening) Yes, I result to this, knowing good and damned well that I can't reach him any more than I can see him! Oh well, she doesn't know that! By any means necessary, regain control of the situation!   :-S

@skatermom can you raise my kids? =-)

I have 5 kids from 3 to 13 and they ignore me to the point of me freaking out...but dad says it once and they do it!  I try to be as mean as him, but they don't buy it. grrrrr  Not sure how to time out once the kids are older.  I give up