Definitely a Mycena. Marasmius elegans is a more robust species with a two tone stipe, white at the apex and reddish brown towards the base. With Mycena roseoflava it is reported to have small stem (stipe) of about 3 mm long and so nowhere near as elegant as your gorgeous little specimen and the cap is chunkier than your one as well. A delightful record of one of the many most probably unnamed Mycena species.