Well, first off... I'm not a huge advocate of females using t3 in general for BB'ing purposes.
Secondly, what's her BBT range?
Is her diet/training/cardio in check?
There are much better (and safer) alternatives than t3 or clen. Don't let her take the easy way out...
Lastly, if she's bound and bent on using t3, begin at 25mcg/day, and bump it up after a week or so to 35-50mcg, and monitor her BBT through-out... ensure/try to keep her BBT in the optimal range. There would be no need to use much more than that (dosage wise)... have her take it in the morning on an empty stomach.