If your friend plans to spend any time in Europe before proceeding to Kenya, it could be more convenient to take a short-term contract with some of European operators. They are very likely to have roaming agreements with their Kenyan counterparts (e.g. both Croatian operators have them with both Kenyan ones). That way she would avoid search for 'scratch cards', and calls would be charged to her European phone bill (and so, presumably, to her CC). Further, intra-country roaming agreements are rare: if using local Kenyan pre-paid service she would have to choose one of their operators. With SIM belonging to an out-of-country operator with good roaming agreements, she would be able to connect using whichever local operator has coverage at the location. This is not an issue in Europe where 95%+ coverage is the norm, but could be in Africa.

Ask her to post some photos!