Don't know much about parenting but I guess you are going to have a major problem with your daughter if you sneak into her room and remove her property. OTOH, it is your house. You can ask your daughter to take her bag with her and move out or get rid of it if she wants to stay.
Or you could change your own mind and develop a closer relationship with your daughter. This is a matter of conscience for you but not for her. I doubt she is a satanist or will become one because of a pentagram. Matters of conscience are important ones, however. You need to realize the problem is not with the symbols but with your conscience. While I respect your disdain, even fear, of things related to the enemy of mankind it is you who are giving those things the power to interrupt your family's harmony. Intrinsically, they are nothing, as Paul said, "An idol is nothing in this world." They have no power, vibration, energy. They are nothing, unless you make them into something.