She must experinece a real Shabbos first before trying to keep it on her own again. Maybe instead of hosting her for Shabbos try finding a Shabbaton you both could go on together. I know Ohr Naava had one recently, but I’m sure there are other places that arrange them too. Maybe try looking in to that.
Also you can try learning the Nefesh Shimshon on Shabbos book together. It literally changed my Shabbos experiences.