Need advice!
My husband and I have two huskies. We've had our girl for about 7.5 years and her brother for a little over a year. The boy, Mavi, is cool calm and collected as can be. His sister, Shea, is a little more on edge at times. We also call her catdog (LOL) cause she can have an attitude sometimes. My brother and sister in law had us watch their 8 month old this past weekend. We weren't sure how to read Shea. She was talking and howling at the baby and when we put the baby down on her level it was almost as though she wanted to go after my niece like a cat. (Of which she hates cats, it's like a game to catch and shake them...honestly, she claimed one cat several years ago). Maybe she was just super curious of what is that little human. Note: We also have my husbands 10 year old daughter part time (of whom she loves) and we have several other niece and nephews that she's used to (and when she's tired of them she goes to a different area to avoid). Maybe it was just me being SO NERVOUS knowing that if Shea started to act out there's no way my 8 month old niece could defend herself like another dog or cat would. Not sure what to think...
One day, my husband and I would like to start our own family. How can we prepare our girl for a possible arrival and new addition? I read that there will be jealousy but they learn to understand the new baby is part of the pack and okay. Was this past weekend just a momentary jealousy thing because I was paying attention to my niece? Was I just SUPER NERVOUS for my nieces safety? Probably a mixture of both.
Anyone have an experience with this? Input? Suggestions? Thoughts?

Your nervousness, the newness of the baby, and what sounds like a lack of real introductions could play a large role in how a dog responds to a baby. Never put a baby on the ground with a dog you aren't sure how they will respond. Proper introductions. If you know you are going to have a child around it helps to have something that smells like the child around a couple days before if possible. So if you know you are going to be babysitting your niece, maybe ask for a shirt or something that she's worn that you can expose your dog to to get them used to her smell before they have to get used to her noises and the weird way babies move. Make them observe from a distance. Don't let them approach baby until you are calm and they are calm. Even then let them sniff calmly with the baby in your arms and make them back away if you become uncomfortable or they become too obsessive about it. I would leave child in a play pen if not holding for the first while so you have that extra barrier of safety while the dogs are adjusting and you are becoming more familiar with their body language.

This is a good thread about getting dogs used to baby stuff in general.

https://www.itsahuskything.com/t9198-advice-from-parents-that-own-huskies

Another one that talks about when baby is actually home.

https://www.itsahuskything.com/t1983-introducing-bear-to-our-new-baby?highlight=baby

When the time comes for you to bring home your own baby things will be completely different. Don't forget she will have your entire pregnancy to note the many changes that come with bringing home an infant. She will take a lot of cues from your behavior, nervousness and signals. I think you will be more comfortable about introductions when it is your own.

My Dakota will go for cats too but he is an angel with my babies. Our first child he got to meet shortly after we brought her home from the hospital. We were very calm and relaxed. I held our daughter to let him have a sniff while we had multiple people ready to step in should anything have gone unexpectedly. He was so sweet, sniffed her a short while and then we lifted her away. He was cool, calm and collected when we brought number 2 home. He actually didn't even care when number 2 joined us. We are currently expecting baby number 3 in less than 2 months and I expect he could care less.