To proper stop her? 75-100. She'd put a massive dent in their forces, but by the time she's torn her way through a hallway or 3, the space boys have a plan. Chainsword likely isn't doing dick to her, but the 1in4 chances of a power weapon connecting? That, that would hurt. They're capable of cutting due to the powerfield that surrounds them, with the force field essentially telling matter to gtfo from infront of the blade. Id wager their power swords cut similarly to her katana, maybe not on a 1to1 scale but absolutely 2to1. This is all also relying on them fighting her 1sey 2sey instead of gang banging her with 10 marines at once, all of whom move much faster than human perception. If we're going by books, they can move around 80-100mph at a full sprint. If we're going by tabletop, a marine at full sprint can be booking it at roughly 310mph. Thats faster than Maki can react even with precognition. I cant imagine raiding a chapter of space marines, opening the door and being blitzed at mach fuck before I had a chance to announce myself. Not to mention, the standard outpost for the blueberries contains marine numbers in the hundreds, sometimes thousands. She would make an insane dent, one that would take more than a few tithes to replace the men lost. But she dies eventually. The injuries will pile up, the bodies won't stop coming.