Finding a Ghul Matron is pretty easy... Contrary to popular belief

If you aim to finish the the Hunting Challenges at the 9th step you'll have to kill a Ghul Matron. If you have finished a story related quest which contains the said creature you'll have to find it on your own to slay it. I also thought they were rare and it would be a pain to find them but I'll show to you that it's the contrary by just explaining a few steps.

Step 1: Find a group of Ghuls

It is easier to find them at night so you may want to advance time in one of the towers and a Carabor may come in handy to traverse eaiser.

Step 2: Fight the Ghuls

After finding the Ghuls DON'T kill all of them. After you finish off the majority of Ghuls they will start to flee (a flashing claw mark will appear on top of them) and after a while they will dig the ground and disappear.

Step 3: Wait

After they dug the ground and disappeared they will appear after a while with a new group. Repeat the second step and kill the majority until the alive few will retreat.

Step 4: Repeat until a Ghul Matron appears

After repeating for 2 or 3 times in the new wave a Ghul Matron will apear besides classic and spitter Ghuls. Now you can go and kill the Matron. (Ranged attacks and/or an explosive resource can help you really well with that task)

Step 5: Bask in the glory of your success

No but on a serious note is just easy as I have showed you. So go and kill those Matrons! Good hunting hunters!