A lot of people reccomend moving up the carb ladder for many reasons. The main one is more food choices.
Your sister might fail if she does not move up the ladder and add more carbs in. She will be bored with her choices and give up. That should be her decision. She has to make this a WOL for her.
If you want to stay on induction level carbs, thats your choice.
She should be able to make her own choice.
That's just my opinion.