You say she "generously" let you use her app so you could get a discount on your ticket. Do I understand correctly: She believed she'd bought 14 tickets and wanted you to buy the final 15th ticket so she could finally enjoy her free ticket before leaving town, but she miscalculated—she'd already bought 15, so the free ticket went to you? Dear heart: There was nothing "generous" about her inviting you to attach your cash to her consumer rewards number so she could rack up rewards points. In economic terms, it was a mutual benefit (because you'd get a discount and she'd get one step closer to a free ticket), not a sacrifice on her part. It was a friendly arrangement, but it was financially self-serving. She was mad because she tried to recruit your help to get herself a consumer reward, the scheme didn't work, and it felt like a small loss to her. A disappointment, perhaps, but a tiny one—and an "emotional void" only if her emotional validation comes from consumer rewards.