I have daughter that comes visits me she also plays OSRS but when she comes over to visit me she can't play hers on my computer. How do I add her to my computer so she can play? Every time I tried to add her we get error pw or email don't match.
Once she's done that, you'll have to completely logout of your Jagex Account in the Launcher, in order for her to login and play on her own. Be sure she completely logs out after so you can play on yours once she's done!
You should never be sharing access to the same Jagex Account, just like you wouldn't want to share access to your single characters before Jagex Accounts. It's a quick and easy way lose account security, plus it's against the rules.
Keep it fun, friendly, and helpful.