Traitorfish
The Tighnahulish Kid
It sounds like you're talking about the huldra, which are primarily a component of Swedish folklore. The English usage of "troll" tends to refer to the Norwegian version, however questionably, which is traditionally treated as a chaotic nature-spirit or wild creature, sometimes associate with the jötun; in one poem, for example, a troll-witch declares herself to be, literally or figuratively, a "giant of the gales".
Of course, this only goes to show how imprecise folklore can be; the Norwegian troll is giant-like, the Southern Swedish troll is perhaps comparable to a fairy, while the Scottish trow, inherited from the Norsemen of the Northern Isles, is a diminutive, goblin-like creature. It doesn't help that, as I said, troll seems similar to "fairy" and "elf" in that it was often used to refer to a broad range of creatures, often a description of nature, rather than form, and only relatively recently came to denote a particular creature. (And the troll is still a broad range even then- when it can include this, this, this and this, you know that there's no real consensus.)
Of course, this only goes to show how imprecise folklore can be; the Norwegian troll is giant-like, the Southern Swedish troll is perhaps comparable to a fairy, while the Scottish trow, inherited from the Norsemen of the Northern Isles, is a diminutive, goblin-like creature. It doesn't help that, as I said, troll seems similar to "fairy" and "elf" in that it was often used to refer to a broad range of creatures, often a description of nature, rather than form, and only relatively recently came to denote a particular creature. (And the troll is still a broad range even then- when it can include this, this, this and this, you know that there's no real consensus.)