Letter: 

"Dear Isabella,
     So at one point in time, I fell for my best friend. we met and clicked instantly, vibes were good and everything but she had a (no good) man at the time. he would cheat on her and she would tell me about it and cry about it. we spent a bunch of time together, went out a couple times because I wanted to treat her how she deserved to be treated since her bf wasn't. I told her how I really felt and after a while, they broke up and we started talking and chilling and things were great until she wanted to run back to her old bf who always did her wrong. so my question is why do girls sometimes leave a new, good relationship to go back to a old, bad situation?"

Response:

 Thank you for submitting your letter to Truth By Bella. Excited that you're the first Blue Letter (guy) submission. Alright so now moving onto your letter, I could identify with your best friend and relate to her cause I was once that girl some time ago. I don't want to go into any details lol. Although you caught feelings for her, it is clear she is more invested in the guy who you claim is no good. You have to think sometimes if it worth loosing your best friend who's in a tough situation to pursing a new relationship. Once you're friends and move into the next step which is a relationship, you can't always go back to how things were. I'm not saying it's your fault. Honestly, would you want to be with a person who isn't over their past completely? However, maybe she doesn't realize if you would be good for her or not. She's probably stuck on the guy because she's hoping he will change one day. I hope I answered your question. It's rare a female would leave a good relationship to get back to a bad one. It's all about foundation & communication! Coming from a person who knows a lot regarding situations like this.