I’m trying to be mekarev a girl to yiddishkeit, she went off the derech, she recently told me she doesn’t promise but asked me if I were to tell you I’ll keep one thing of yiddishkeit what would it be? She also wrote that I shouldn’t answer shabbos, kosher, or modesty or being shomer negia, what should I tell her?
I would suggest prayer (shemoneh esrei). Explain to her that prayer is not merely an act of requesting one’s needs and desires from Hashem, but rather an act of relationship with Hashem. When one prays, one declares one’s faith in Hashem, one’s trust in Him for all the aspects of one’s life, and one reciprocates in the modim blessing, thanking Hashem for all we have. I know several people who are not fully observant, but they have a close “relationship” with Hashem through prayer. Please G-d, this closeness will make the way back nearer and easier.