Middle-earth: Shadow of Mordor - Game of the Year Edition

Missable due to no matrons spawning after the DLC missions are completed. But there is a way to get it quickly if you did miss it in your first play through. No need to triy
To have them spawn wave after wave.

The easiest way to do this is in the right after the first mission of the hunt where Torvin teaches you about Caragaths. Travel to the south west corner of the map a no accept the hunt mission 'Matrons Rising'. Make sure you have full arrows. When you reach the second ghûl nest a matron should spawn. Shoot 4 regular ghûls with regular arrows and then hit her with your fifth arrow shot by selecting the fire arrow (RB). This should light her on fire.

If you missed the acheivement on your first play through as I did, simply go to the main menu and select save slot. Start a new Lord of the Hunt playthrough and run as above. No need to delete anything or play through more than one full mission.

You can still get this while being in the Lord of the Hunt campaign. At one point you will have to fight one of the Warchiefs. His name is Ûgakûga Graug Rider. As we know by now, you need to lure out the Warchief before he will show up. You have to shoot several Ghûl mounts to bait them.
I might have been lucky, but there popped a Ghûl Matron out of one hole (Taller than regular Ghûls, spikey skin) . I pressed , boosted my combo score to 5 with a regular orc and fired on the Matron. It died, I got the achievement.

You have to act very quickly, because the map will be SWARMED with Ghûls in no time (They will attack the Graug at an alarming rate)

Just to add to the above solutions, it does not actually matter how you set a matron on fire, only that you do. You can explode campfires and grog barrels if you can lure them close to one.