Can't you find her a bike that will make her want to actually ride? Unless she plans to ride the bike off-road she will get much more pleasure out of a bike that is more sensible for the purpose. I have always maintained that the use of mountain bikes on road have discouraged more people from riding regularly than anything else. When used for their intended purpose, MTB are great, but when used for other applications, they are about as wrong as you can get and encourage people to not look after their bikes like they should.