It is the perfect wrong time for Jeremy to do to Mirabelle what she had done to him - call him up for a quick fix - because;, in a sense, she is now betrothed. Her first date with someone who treated her well obligates her to faithfulness, at least until the relationship is explored.
In the narrative of "Shopgirl," Jeremy is faced with a dilemma as he contemplates rekindling a relationship with Mirabelle. The situation is complicated by the fact that Mirabelle is at the start of a new romance with someone who has been treating her nicely. This new connection leads to a sense of obligation for Mirabelle, suggesting that she should remain faithful as she explores this potential relationship.
This turn of events...