Xiomara’s mom has some pretty straightforward rules when it comes to dating. First, she can’t date. Second, not until she’s married. And third, see rules one and two.
Later on in the book, Xiomara provides us with further clarification of her mom’s dating rules, which make them seem somewhat more reasonable—or less ridiculous, depending on how one looks at the matter. For as long as Xiomara can remember, Mami has always told her that she cannot have a boyfriend until she’s done with college. And even then, she has very strict and particular rules as to what kind of boy he should be.
So that conclusively rules out Aman. He clearly doesn’t fall into Mami’s category of what she considers a suitable male companion for her daughter. And of course, Xiomara hasn’t even started college, let alone finished it. With pardonable exaggeration, Xiomara reckons that going to the park alone with Aman might as well be the eighth deadly sin for Mami. But she can’t wait to go with him anyway. What Xiomara calls her mom’s Rikers Island prison-like rules may well be "scripture set in stone," as she puts it, but that doesn’t mean that she’s about to follow them.