Hi @Buddyboo and I'd also like to welcome to our online community!
It's so good you've identified this trait in your daughter when she's young and she has a better chance of working through it and learning how to let go. My mum has held onto things people have said to her over 50 years ago and doesn't let them go and it would've been great if she'd addressed this as a young person. There are a few classic sayings about letting go such as "pick your battles" and forgiveness is an important process, which is much more important for the person doing the forgiving and issues don't fester like a cancer or infection.
The other aspect of this is why she feels the need to hold on. Does she like to be in control and are there things in her life which are feeling beyond her control that are concerning her?
Dealing with anger could be another aspect of this situation.
Maybe learning so simple relaxation or mindfulness techniques might help. Going for a walk or a run. Visualising the situation dissolving or disappearing like a helium balloon into the sky might help. When Reachout first came into being, they used to have a rocket in the teen's section and they could write their problem inside the rocket and then press a button to send their problem into space. It seemed like a great idea to me.
I hope those suggestions help.
Best wishes,
Birdwings
