I have a beautiful, intelligent, red-headed 3 yo daughter. She is my first born and I love her with all my heart. However, she is becoming more and more belligerent with each passing day. I included the fact that she is red-haired as I am familiar with the stereotype of the fiery red-head. Is this just the age for her to be asserting herself or is it a behavior problem that needs attention. She also has an 7 yo half-sister she gets to see every other weekend and an 9 wo baby sister that is getting some of the attention she used to get. She is also wetting the bed again.

Any insight would be greatly appreciated.

I going to guess it is the 9 week old. She probably feels her territory is being infringed upon by the new baby. You will have to stay in control and be calm and firm with her when she is having a tantrum. I'm sure it will get better as the newness of the "threat" wears off.

She's wetting the bed again. Ah, the wonders of regression (wetting after being fully potty trained). LOL

So, you have a 9 week old? Did this behavior, including wetting the bed, start around the time that the baby was born?

This is common among children of this age, especially when there is a new baby. She needs some Mommy time, if you aren't giving it to her already. Just you and her. She is regressing because of the new baby and the attention the baby gets.

She is acting out to get attention. Children of this age want attention, they don't care what kind. If you are yelling at her because she did something bad, she's still getting attention. Good or bad, it's still attention.

Now, though, you are the parent. You must set limits and stick to them. You have to be firm, yet loving. Consistency is the key when it comes to children.

I also agree with the above answers and feel this is probably happening due to the new baby.

Have you allowed her to interact with her new sister?

I allowed my daughter, who was 3 yrs old at the time, to be a big sister and a big mommy's helper when my son was born.

I'd let her hold him in her lap, hold the bottle while he was eating, pick out his cloths, help change his diaper, sprinkle the baby power, etc,etc...

I took lots of pictures of both of them together and would make a big fuss over what a beautiful big sister she was
And gave her a little photo book filled with pictures of them together.
She was very proud of her pictures and loved showing them off to anyone that would look.

Everything I did with her before my son was born, I just continued on doing except with a baby in my arms... LOL

It was really quite simple and my daughter never had any of the set backs that some children do when a sibling is born.
I'm not absolutely positive that including her with everything contributed to good, helpful behavior or if that was just how she was on her own.

Just try including your daughter in everything that you do for your new baby, ask her if she'd like to help, or if she asks to help say yes.

If she feels that her new sister "needs a big sister" and mommy "needs a big helper" and she has a "responsibility",
Her bad behavior may turn around as she must "set a good example"... It's worth a shot... it worked for me... I think.

Congratulations on your new baby and good luck with your 3 year old...
Mine are 3 years apart... You're going to have lots of fun when they are 7 and 4 ;) :D