Strider Clutchmother can be found with NPCScan. You will need to add it, her NPCScan ID is 2172.
You can also use this macro to help find and tame her:
/tar Strider Clutchmother
/cast Tame Beast
Although she is rare, she is on a very short spawn timer. It looks like her timer can be as short as 10 minutes since she was last tamed or killed.
I'd also like to note that when you start taming her, her hatchlings will attack as well. I tamed her with a lvl 14 in decent gear (boa's) and was still taken down to about 50% health. So do be careful if your taming her on a low level toon.