<human>: So earlier this year I pulled the trigger on the process of getting an engagement ring by buying the custom stone I wanted from a specific gem cutter. It was in hot demand, it was the one I wanted and I didn't want to wait for something else to come around.

Anyway, this was a large purchase and I wanted to take advantage of it by putting it on a couple of credit cards with a sign up bonus. This is kinda where a problem has come up. My girlfriend, who lives with me, noticed my new cards and wanted to know what I was doing to meet the sign up bonuses and I didn't know what else to say other than, "its a surprise for your birthday" (which was 3 months away). I really didn't like lying to her but I didn't have anything else to say without causing more doubt. So that kinda got me off the hook.

So now this week she came into my office and jokingly started to read the subject lines over my shoulder of my emails and I snapped at her not to because I had been talking via email with the gem cutter and jeweler. I didn't want to ruin the surprise and asked her to respect privacy boundaries when it came to my email account. She is not the one to really go through my email account, she was doing it as a joke but now she is super suspicious and sent me an email with things saying that she feels like I am being too secretive and that trust and security in our relationship isn't as strong as it was.

So my question is that, how can I safely defuse this potential time bomb without ruining the proposal surprise or should I just scramble and purpose ASAP? I personally would like to wait for a significant date later this year but I am concerned when she is thinking something is wrong in our relationship.

Can you condense the text into a few key points?
<bot>: Made GF suspicious during the buying process of an engagement ring and looking for advice on how to diffuse her suspicions or just propose before I wanted to.