I am expecting my first child and my foster daughter is having some issues. She is usually well tempered but since we told her about the upcoming baby she has been very moody. Has anyone else ever dealt with this? We already explained about loving them both the same and that she isn't going to be replaced.

I assume this is a sign of jealousy from her and I also think that in a way it's natural. Just keep on being the awesome parent you already are and try to involve her little by little into the new member's life. I think a kid would love to see that 1. he's still your pride and joy and 2. the new one is not an "enemy", but someone to love and take care ... It's a difficult time indeed, you need all the diplomacy and love ;)

You don't say the age of your foster child.....Try to 'really' involve them though, like asking 'what shall we name the baby'', ''you are going to be such help to mama, how are you going to help me take care''....I'm a little worried too though, as a 'foster' does that mean that this child WILL leave your care? If so, then the child in their mind, might think the baby is the reason they are leaving NOT the 'system' you know what I mean?

It's totally natural. I was once given this analagy. Imagine your husband coming home one day and telling you he was getting another wife. Switch all of the things you would say to a child, only use yourself in the place of the child.

"It'll be OUR wife. We'll love her together"
"I'll need you to help with this new wife. Teach her things and play with her"
"I'll have room for both my wives. I'll love both of you equally."
"I'm not replacing you, honey, I just wanted another wife to love as much as I love you"

No matter what you say, she'll be jealous. That doesn't mean stop trying. She will figure out she's not being replaced. It'll just take some time for her to get used to it.