She should be able to play. Just not install the games.
Control panel, User Accounts, User Account Types will tell you the subtle difference between Limited User and Admin accounts.
Do you mean she doesn't have an icon under her account to play the Sims or does the system prevent there playing it?
If its missing icons you can copy them by right clicking the Start Button and choose "explore all users" Then move / copy icons about the Start Menu trees as you see fit.