I haven't seen that client apps - games, office tools, Internet browsing, etc are any harder for Linux than Windows. Maybe admin tasks might be hard for someone to absorb - but once set up, how many of those would she deal with anyway? That'd be YOUR headache, no? *chuckle*
Set up the box to dual-boot, but give her an account - ask her to use Linux when she can, rather than rebooting (for things like browsing, mail, etc.)
Who knows - she may grow to like it better!