Definitely STAY AWAY from any more hormones bro. Adding in more T3, without a doctor's supervision, could suppress her even more. My sister has hypothyroidism and is currently taking T3/T4 and she hates it because not only does she not get the effects of a higher level of T3/T4 (weight loss) but she does get the constant lethargy, trouble sleeping, etc. that I get and I have mild HYPERthyroidism.
I would honestly have her speak with her doctor about the weightloss program. He might be able to run some tests and allow her a slightly higher dosage or something.