Tree Stride. Once on her turn, the dryad can use 10 feet of her movement to step magically into one living tree within her reach and emerge from a second living tree within 60 feet of the first tree, appearing in an unoccupied space within 5 feet of the second tree. Both trees must be large or bigger. (MM p.121)
It's obvious that the dryad will get out of reach of a melee assailant. But is this considered a teleportation? Does this movement provoke opportunity attacks? Keep in mind that this ability is not listed as an action.