Butthole Before Vagina

My first gf was a sweet girl who promised her mom she wouldn’t have sex and meant it. I explained to her I was ok with it but still had needs and eventually was ok sucking me off and letting me play with her tits. I told her multiple times I wanted to finger her or eat her out but she guarded her pussy. One day some of our friends had a pool party and we were alone in a pool after everyone got out. I made out with her and tried to finger her again. She stopped me when I got near her vagina so I went from behind and started to feel her butthole. She didn’t stop me. I stuck a finger in her butt and it was extremely tight. She didn’t say anything the whole time and would get too embarrassed when I’d try to bring it up later. From that day on she would let me play with her butthole. I never got to fuck it unfortunately but i loved feeling how tight it was