The sister and cousin were part and parcel of the misunderstanding, but can't be held totally responsible since they were children at the time. The FL shouldn't have relied on them, but she was only fifteen years old herself and good judgment for situations like that was still years away for her. The mother was the one who forced her to give up her daughter, was the cause of her meeting her "boyfriend" in secret, and was still treating her like garbage 15 stinking years later. She was also basically licking the hated boyfriend's boots while still treating her daughter like trash. Then we come to the ML. Just how old was he when he was busily impregnating a fifteen year old? I didn't notice anything in the story about his age, but if she wasn't around for long enough for her pregnancy to show and give birth, even if he was a brat, he should still have had something of an idea that he MIGHT have caused some consequences with unprotected sex. Waaaaay too many loose ends in this story, and NO redeeming characters.
THE BRIDESMAID'S SECRET