<human>: Summarize the given text in a few sentences.

I don't want to get into details, but I'm sure many have been in this situation so I can probably get solid advice on the details.

I'm in a relationship that has become more serious over time, and the person has asked me from time to time about previous relationships. I figured it would be important because of some of the people I've been with she knows. I've told her everything, including details about people she knows pretty well that took her a long time to get over.

Well, everything except one. It wasn't a big deal, it lasted for a very short period, and all we did was make out. The thing is, because of how much she struggled after telling her about all the other relationships, I just lied and said nothing happened. She's heard rumors otherwise (that we made out) but believes me. It would cause a lot of unnecessary heartbreak to tell her.
<bot>: lied to my girlfriend about making out with someone else years before we were together. Told her lots of worse things, didn't want to make her feel bad yet again. Acceptable?