We travel at least once a year outside the U.S., & rely on wifi for text messages, email, & data. iPhones & iPads stay in airplane mode for the entire trip. We haven't used Skype much, but this allows "phoning" via wifi; both parties have to install the Skype app & both must be on when the call is made, so the time has to be prearranged. If the place(s) we go to do not supply reliable & free wifi, we have rented a small mifi unit that converts local cellular into wifi data at about $15/day, but this would be really expensive for longer than 2-3 weeks. We never use internet cafes -- too dicey & often difficult to find & use.
Cellular calling across countries is expensive, even with international plans. However, ATT has just introduced its Passport plan, which has better rates than previous plans, but is still not cheap.
A local phone only solves the problem of local calling; calling across countries is expensive regardless of which phone is used. We do very little local calling, so we never get a local phone. Instead, we ask wherever we're staying to help with reservations, etc. This helps with language problems as well.
My recommendation is to get really familiar with what she can do with wifi, texting, & maybe Skype before she starts traveling. If absolutely necessary, she can place very quick cellular calls if timeliness is important, but it rarely is. She needs to turn off her cellular service except when she absolutely wants to call. Everyone else should text or email her.