Xbox Console/Controller Issue

Hello Zainniaz if its specifically the right analog it could be that the controller needs updating, for this you can go on your console settings in the devices and streaming section and go on accessories from there your controller should come up on screen
and if you press the ellipses which are shown in the brackets (...) then you can see if your controller is up to date. whereas if its only slow in games then it could be the in game controller settings or sensitivity.

Do you have anything plugged into your Xbox? Like a wired controller or keyboard perhaps? If so it's possible that may be interfering with your controller inputs.

You could also try loading up the Xbox Accessories app while on the console to configure the controller.

I must say, really, really weird. Try
power cycle your console.

Try remove and then add her account again after that. Are you sure that you didn't changed something with controller on her account?

After having controller issues myself over the years, I wouldn't think that it was the console. If after going through the link that I originally included you don't notice a difference, you could try another controller if you have one. If the same issue
happens with that controller you could see about getting your console serviced.

I would remove her account and add it again just to see if that changes anything? Are you sure she didn't change any of the settings in the game that she is playing? Sometimes if you increase the sensitivity of the camera in a game, it might seem that
there is controller drifting.