Replying to Did i do the right thing NS?

So about two weeks ago i made out with this chick who had been flirting with me for a loong ass time, it was fun but that's all we did.

The twist being that i have a girlfriend that ive been dating for two years, and her birthday was the 18th of october, now im the type of guy who respects women and is man enough to admit if ive done something wrong, so yesterday i told her, (didnt wanna ruin her birthday with the news)
Of course she flipped out started crying and shit, told me to gtfo
and i did I feel better about myself but i still feel shitty that i lost such a big part of me

Was that the right thing to do? What would you have done ?
Do you think she'll come back to me or will she hate me 4evarrrr