Here's what you can do to turn this around:

**Acknowledge it directly** — Own the mistake without making excuses. A simple "Hey, I know I ate the cookies and that was thoughtless. I'm sorry" goes a long way. People appreciate honesty and accountability, especially for small things.

**Make it right with a replacement** — The easiest fix is to replace them. Grab her favorite cookies or treats from the store, or if you're feeling ambitious, bake a fresh batch yourself. Even store-bought ones show you put in effort to fix it.

**Offer context if relevant** — If you were really hungry or just grabbed them without thinking, a brief explanation can help, but don't lean on it as an excuse. Keep it short: "I was starving and just mindlessly grabbed them without thinking" is fine; don't over-explain.

**Check in on her** — Sometimes the issue isn't really about the cookies—it's feeling like your stuff isn't respected. Ask her: "What can I do to make this right?" or "Is there something specific you were looking forward to about those cookies?" This shows you care about her feelings beyond just the snack.

**Look ahead** — If this is part of a pattern, suggest a solution going forward. Maybe mark certain snacks as "yours" or agree to ask before eating shared food. Small agreements like this prevent repeat arguments.

The good news: **this is a pretty minor thing** in the grand scheme of relationship issues. A sincere apology plus replacing them should clear it up quickly. Don't overthink it, but do show you're taking her annoyance seriously.