Hi
My plan of action for this type of patient is to exclude muscle tightness away from the symptom area in the Lx. As piriformis is tight, try a very deep piriformis friction massage (even to the point of bruising the skin). The patient must be warned, and be careful if they bruise easily or are on blod thinning medication. It is imperative that gluteal and hamstring stretches are given after the treatment, and even if she is in pain the exercises should be done at home 4-6 times daily, 5 repeats, for at least two days. she must not sit around, but keep moving, or tethering can reoccur. Sometimes a prone knee bend test can indicate that this treatment will be of assistance - but not always.
Also, check the ileopsoas length, and stretch if necessary.

If the above is unhelpful, the problem could be central.
Regards
MrPhysio