I did this three days ago. Spent til the early hours of the morning doing it, and i used an old power armour, which already had an arm and leg on the left hand side destroyed by some blobby fishes and a deathclaw i met on the way.
I am playing it on very easy though, so it isn't too hard. I downloaded all of my shotgun shells in the castle, in the sergeant who you meet in the dungeon, then when it came to the queen i used three missiles and some sniper caps to take her out. Although Preston from the minute men, fired the closing shot.
And her babies also kept me busy, having to constantly look down in case that they were coming at me as well. A job well done?!?
Should I still go?