We actually see her clean some of the blood up, and we also see some blood she doesn't on the railing. However, the bloody message on the mirror is a big question. I've surmised that she cleans that up also at one point and we just don't see it (I put it in my Triangle Matrix spreadsheet as a side-note). In fact, she'd almost have to. Otherwise, it'd still be there. But you're right, the movie doesn't cover the bloody mirror message, which wouldn't reset. Therefore, it must be cleaned up at some point. Really gonna miss IMDB message boards.

I'm something new entirely. With my own set of rules. I'm Dexter. Boo.

What about the blood on the mirror and everywhere else?
It comes from outside and shouldn't reset the theater should be a pool of blood

Like the other guy said. That's why we see the food is edible, then mouldy, then edible again. This answers any questions about axes and shotguns being in their proper place when they're needed.
(Done with fish.)

Everything native to the Aeolus environment "resets" (or more accurately, appears to reset when entering it at a time prior to things there being changed). However, anything external or foreign introduced to it accumulates, being orphaned in time, so to speak. A lot more than just the shotgun resets. Everything on the ship does. What doesn't are items brought to the ship from the outside world on board the Triangle yacht, including the people.
For crazy in-depth discussion feel free to peruse:
http://www.imdb.com/board/11187064/board/thread/223982092
http://sdrv.ms/MoXetr

I'm something new entirely. With my own set of rules. I'm Dexter. Boo.