Have you asked her what she did to relieve the pain last time? Did she receive any formal therapy? Did they give her any exercises to perform?
Sciatica can be tricky. There can be so many different causes and depending on the cause, depends which exercises you’d want to do to treat it.
When a pregnant woman presents with sciatica, we often advise them to do opposite arm and leg extensions in an all fours position, cat/cow stretch and bridges. These exercises help to relieve the pressure of the baby on the sciatic nerve, however, the only way to get rid of sciatica is delivery.
In your case, I’d ask her the questions listed above and then have her follow up with a physician to get to the root of the cause.