(((((chalmette))))) they are right, get the piece of paper

even here in Aus it works like StarPonysMama says

there are people at the courts to help you do it right

the police will arrive much more quickly if you have a restraining order, also they will arrest her, something our police can't be relied upon to do if the intruder is know to you, unless you have the order

if you're lucky, having the papers served on her will put her off

best wishes