Help with Possible Sciatic Pain

I’m looking for some input here which I can hopefully pass on to my Mum. Recently, she’s been experiencing a lot of pain which she is comparing to sciatica (which she has suffered from in the past,) and it seems to only be getting worse. Considering the past 2 years have seen her go through hell with a severe case of frozen shoulder and numerous medical procedures to treat it, I’d really like to try to help her out with her hip.

A bit of info… She suffers from no lower-back pain, which has me thinking that the problem is stemming from an issue with the piriformis. She claims to be particularly tender right up by her right S.I. joint, which has me further considering the piriformis (I believe it attaches into the joint?) I had her trying to ease onto a soft foam-roller, but she could barely manage it, due to how tender it was. I have shown her a cross-body stretch for the back of the hip, but when she eases into the stretch she starts to complain of a cramp in her anterior hip- the location she cites is difficult for me to know whether it may be hip flexor or adductor. I’m wondering however if an issue in a muscle within that region may possibly be affecting the piriformis on the other side of the hip joint? Or is there a possibility that the piriformis is attempting to pick up the slack of an underactive muscle group?

If anybody out there can chime in, I’d hugely appreciate it. My Mum’s been through a lot of difficulty already with her shoulder, and I’d hate to see her have to try to cope with this too.