Hey there,
Sorry to hear she's not feeling well...
My son has been on Pentasa for 3 years now. The only time he's been off of it was when his GI wanted him to try Lialda (he takes 3500 mgs Pentasa per day - 4 pills in the am/ 3 pills in the pm) and she thought it would be easier for him to deal with only 3 pills of Lialda per day. Needless today within a week he felt different, by week 2 he was exhausted and experience a cramp. I switched him back to Pentasa immediately (contacted the GI the next day and told her what we were doing. Because we were "trying" the Lialda she was cool with it, and he was back to his "normal" within a week or so.
It is probably best to call the doctor on Monday and confirm before restarting them (especially if you didn't have an agreement in place prior stating, "If this happens, start taking meds again.")
We don't have any experience with Imuran - did the Imuran replace the Pentasa?
I hope she feels better soon!