I have it on good authority that Stu is
not sane but this has nothing to do with his knowledge of GSM roaming.

Really, you can't prove a negative. It's possible that there was some mistake that allowed her to have free calls in India. For years T-Mobile didn't charge me for roaming (at all). All you can say is that none of us here have found any SIM that claims to provide free incoming calls in India.