I'm doing the mission called Cambridge Polymer Labs and after I use the computer to unleash the facility defense system, the turrets go online and Molly starts attacking. What do I supposed to do so Molly doesn't attack?

You are supposed to create a Power Armor Chestpiece. There is a recipe on the terminal to the right after the cleanroom.

Yeah, I you set it up so you can leave the lab prior to finishing the experiment she will attack.

i walked it and shot everything to sh*t straight away, i didnt know there was a quest still made the chest piece but its not as good as my X-01 mk. VI anyway but was fun to do

From what I understand, Molly is hooked up to that facility's defense systems, so if you set them to attack anyone in sight, she will also attack you as you exit. Try turning off the defense systems before you exit the experiment chambers and see if she acts normally, otherwise I'd advise not activating them at all.

I stumbled upon this location just through a random wandering, so I didn't know what to do, but Molly attacked me too. I think it's because I chose some sort of defense option when I was quickly accessing the terminal. I tried to undo it, but it was too late. I think that's why she turned hostile. Also, the chestpiece should have been something really useful. Basically radiation increases your action points. ehhh...not really worth the trouble. Oh well.

I don't even use my power armor anymore. Totally done with it. It was fine when I was a noob, but at level 65, it's just an ornament.