Isolation.
Ron was devastated. The fact that Annie wasn't his was bad enough, but Draco Malfoy being her father? Talk about rubbing salt into the wounds.
When Annie came over and tried to climb up on his lap, Ron turned away. Unperturbed Annie tried again. Ron turned away again. When he turned away a third time, Annie began to cry. Ron instantly felt bad for making her cry. And realised she had no control over who her father was and that it was wrong for him to take his frustration out on her. From that moment on he made a point of treating her no differently than Rose or Hugo.
Molly on the other hand was not so kind. She ostracised Hermione and Annie for what Hermione had done to Ron. She stopped knitting things for both and gave them meagre servings at mealtimes while ignoring any pleas for second helpings. She refused to get presents for Annie on birthdays or Christmas and for years ignored them both. Making everyone uncomfortable.
The kids, however accepted Annie as part of the family without question. They always tried to make her feel accepted and to make up for Molly ignoring her.
2030 signalled Annie's 10th birthday and by Christmas Ron had had enough of the way Annie and Hermione had been treated. He had it out with his mother. A huge fight in the den. It didn't change her mind. Christmas was the same as it had been for years.
A few months later, just before Annie turned 11, she let Molly know the truth about how she had felt all those years. She explained how on Christmas night just months before she had taken a knife up to her room and slit her wrists. Lily Luna had found her and called the rest of the kids. Victoire, half way through Healer training, had healed the wounds and kept a constant eye on Annie through the night. When Annie had woken in the morning she had begged the kids not to tell anyone. She hadn't wanted Molly to feel like she'd won. Molly listened, then left the room without speaking.
A few days later on Annie's birthday, Molly was nowhere to be found. This wasn't unusual as she often went elsewhere while the family celebrated. By nightfall she still hadn't returned and Arthur started to worry.
Finally just as they were cutting the cake, Molly walked in, arms full of shopping bags. She had spent the whole day shopping to make up for ten years of ignoring Annie and Hermione. As Annie hugged Molly for the first time ever, she told Molly she didn't need all that stuff but Molly told her she'd felt guilty when she found out Annie had tried to kill herself over Molly's behaviour and treatment of her.