Thanks for query,
Weight of your baby at this age must be round about 8 to 8.5 kg so not much less as she is having 7.4 kg.
Montoux test may give positive result if BCG vaccine
so as your doctor has given tab Isoniazide, he might have confirmed the diagnosis by doing X ray
chest,complete CBC etc.If not then get it confirmed by doing all these.
Your diet regime given to your daughter is fine.
Ok and bye.