EA Standard: Not sure at the moment. I think they are supposed to, but I don't know how reliable this is. Sims don't really age-up in worlds not being played, but if their age totals are incremented by one every night at midnight, then their status is supposed to catch up with them the next time they appear on screen (in their world or yours as a guest/tourist). If the sim is technically really still a child, you may find that they cannot travel so they may not be able to be invited over.
NRaas Traveler: Either way, depending on how the mod is set for Ageless Foreign Sims. Ageless is off by default. And children can travel if you allow them to.
If not using Traveler, probably the best thing to do is a Save As, invite her over (if you can), see what happens, and be prepared to dump the save if you don't like the way it goes. If you have MasterController and use its Invite Over function instead of a phone, you don't have to wait days for the foreign guest to arrive or decide at the last minute that they can't make it. :)
