Ok I get it that our MC F-ed up by not saying anything to her about this world dangers, but HOLY SHIT IS SHE STUPID?!?
Ok ok benefit of the doubt maybe she didn't read any manga and didn't played any video game to know that other worlds are dangerous, BUT we have our MC how said "I wear that... when I'm active in this other world..." pointing a bad-ass full plate armor on top of what he can do (jump out of a building without revising any damage ETC) meaning even he need protection here, so clearly this place is ultra dangerous, but NOOOOO