If there is complete, 100% no-contact, then you can realistically expect "hard withdrawal" (near-depressive state, laying in bed, calling in sick to work, etc.) to last from 1-4 weeks, depending on how deeply involved the two of them were. TOTAL withdrawal will happen in fits and starts, gradually improving, and take anywhere from 6-24 months, again, depending on how deeply involved they were.
If she breaks the no-contact, then each encounter with OM will set her "withdrawal clock" back to near 0:00.
