Take the hint, she does. She doesn't allow herself to be shocked (ha) at the sudden help, taking full advantage of the moment to plunge her blade into the stunned monster and finishing it off. She turns to acknowledge her sudden, mysterious helper, but then it's right back to fighting. Thank goodness for the help, yes, but there is also imminent danger. Stupid as taking on a small mob of monsters alone may be, Marie isn't stupid enough to let her guard down while there's still enemies that want her dead. She'll thank this guy once the monsters are dead and not a moment before.