Fixing this relationship is going to be extremely difficult. You need to be completely honest and show deep remorse. Give your girlfriend time to process her feelings, and don't push her to forgive you right away.
Apologize sincerely. That's the first step. Tell her you know you made a huge mistake and that you're deeply sorry. Then, give her space to process her feelings. Don't pressure her to forgive you right away.
First, be respectful. Always use polite language and show that you value her opinions. For example, when having a conversation, listen attentively. Second, show your positive qualities. If you are helpful around the house or are good at something like cooking, share that. Third, be honest and sincere in your interactions. Don't try to deceive her just to get on her good side.
Be honest with your girlfriend. Tell her exactly what happened and how sorry you are for putting her in such an awkward position with her mother. Listen to her reaction and be prepared for her to be angry or disappointed. Assure her that you will take steps to ensure this kind of situation never occurs again.
You could offer to tell the sleeping stories yourself. This way, you can ensure that the story is actually soothing and conducive to sleep.
One way is to encourage open communication. For example, you can plan some family - oriented activities like having a dinner together where everyone can freely talk about their day, their dreams and interests. This helps in breaking the ice and building a more comfortable and friendly atmosphere between them.
Find out what their hobbies are first. If it's something like knitting, you could ask them to teach you the basics. Just show your enthusiasm and eagerness to be part of it.
To fix the relationship, you must start with honesty. Sit your boyfriend down and tell him everything. Expect him to be angry and hurt. Then, give him space to process his feelings. You can't rush him into forgiving you. After that, if he's willing to talk, listen to his concerns and be patient. For example, my friend was in a similar situation. She was honest with her boyfriend, and although it took a long time, they eventually worked through it because she was committed to changing and rebuilding trust.
Maybe she just doesn't have the knack for it. Some people are not good at being creative or engaging when it comes to storytelling. She might not be used to telling stories to others, especially for the purpose of helping someone sleep.
Spend quality time separately with each of them. Take your mother out for a shopping day or a nice lunch. And with your girlfriend, plan romantic dates. Respect their boundaries and individuality. This way, you can build strong and healthy relationships with both.
Just be honest and face her. Apologize sincerely. She may be angry or shocked at first, but your honesty will help in the long run.