My husband and I have no idea the "correct" way to handle our 3 year old acting out.

I'll try and sum this up as briefly as possible. Our 3 year old (4 in March) has a really nasty attitude suddenly over the last 2 months. I'm sure this is very normal behavior for a 3 year old to start acting out, we just aren't sure how to parent it and looking for any suggestions for what has worked for others.She will constantly tell us no. We say clean up your room, put this away, come eat lunch and its always NO. She'll walk away, we'll tell her to get back here right now, and she says NO, I DON'T WANT TO BE A GOOD GIRL! We normally remove anything she is playing with, and put her in a "time out" which really just makes her cry for 3 minutes, and she'll have her attitude right back.We've sat her down and tried talking to her about this. We ask her why she is getting upset and telling Mommy and Daddy no, and she said because she is mad. We tell her it's perfectly fine to feel mad, but it's no reason to get upset and yell and that instead just tell us what is upsetting her and we'll work to fix it. She will sometimes just say "OK mommy" after that, but it goes right out the window 10 minutes later.I work full time (mom), and my husband watches her everyday instead of us trying to afford day care. He says when I am at work, ALL DAY she is an absolute angel and her attitude starts as soon as I get home and usually all day on the weekends when I am home only. Why is that? Why only when I am there?I am 9 months pregnant right now, set to give birth next week and I am wondering if the idea of her new baby sister coming along has gotten her upset. We try and talk about how she can help feed her sister and help take care of her, and generally let her know that it's so exciting we're going to have her come home with us just to try and prepare her a little bit. So I'm not sure if that is something that has changed?Long story short.. she just has a terrible attitude a lot of the time with me anyway, and she doesn't listen. She'll destroy her room when she is in one of those moods, she'll throw things etc. My husband and I just have no idea what to do with the tantrums or the most effective way to get her to relax. We normally will just put her in time out, take toys away or try to talk to her about them nicely. Unfortunately, I am really stressed right now and I've yelled at her quite a bit because I just can't handle it sometimes. I know that's counter productive, I really do try my best to keep my patience I am just so ugh right now being so pregnant and uncomfortable.So what's the verdict? Just flat out ignore her tantrums? Thanks in advance.TL;DR: 3 year old suddenly acting out with an attitude, yelling and throwing things only when Mom is home. Mom and Dad not sure how to handle most effective way. Looking for solutions. via /r/Parenting http://ift.tt/2v6EtxZ