My mother-in-law knows about my severe allergy. She tried to sabotage me anyway.

Dear Prudence is Slate’s advice column. For this edition, Leah Prinzivalli, a Slate features editor, will be filling in as Prudie. Submit questions here. (It’s anonymous!) Dear Prudence, Recently, my mother-in-law came for a visit. I am seriously all... [4568 chars]