I compared roaming rates with a U.S. SIM card with local rates for Kenyans. If she had a T-Mobile SIM, she'd be paying $5/minute. Ouch. If she went with a local SIM card, she would spend roughly $2/minute to call home to her husband, who could then pay $0.67/minute to return the call. At that point, she would only consume her prepaid air minutes.

As far as I can tell, "scratch cards" are sold all over the place in Nairobi. The hard part is finding a SIM card. It looks like she would need to find a dealer for one of the local GSM providers.