My Very Stubborn Two Year old

[phoebeanddaphne]

Both my girls were babywise baby's and have both done very well with schedules up until now. My two year old is very independent and has refused to take naps, this is okay by me we've just worked a new schedule to an earlier bedtime and she goes down like an angel (as long as the light is on) however her lack of wanting to take naps has made my one year old think she doesn't need one either and as most will agree 15 mnths is an age where she still absolutely NEEDS naps.
How do I get my 15 mnth old back on schedule when she knows her sister is on a slightly different one. And wants to be just like her big sister.