Hey Fabian,
This is a great question and something I’ve come across many time throughout my coaching career and it’s always a challenge. The biggest area that often holds back players who are talented and have ability is the mental sod eof the game which is very underrated and extremely important.
Firstly you’re doing the right thing here by looking for ways to change and improve to help her, that’s so important.
Definitely the video recording that you mentioned is a great way of showing what caused mistakes and also that slowing down and looking for more consistency will help. Sometimes the player needs to see it for themselves and not just be told it.
I think you cam also do drills with her the work on the fundamentals like drives, topspin’s, pushes and open ups and give her a number goal, so for example you have to get 20 in a row and if you miss you start again from zero. This will add a match type pressure and give her a focus of consistency. Of course too much of this can get boring so try to mix this in with some more fun drills or matches as well if possible.
It’s also good to set short, medium and long term goals with the players and sit down with them to decide these goals and the areas they need to work on to improve and reach them. In this situation you can put the emphasis on having a strong mind and trying to be solid and hard to beat.
Lastly another drill for you which keeps things fun for the player too is simply free play doing 2 serves each however, she has to put the first 5 balls on the table before she can attempt to win the point. This way it keeps her focus on consistency buy then still has the match and free play elements which are important too.
I hope this is helpful for now and anything else or other questions please let us know.
Cheers, Tom
