Can my daughter sue her ex-boyfriend for taking her car and totalling it 7 months ago

Did she let him borrow it? If she did, then she cant sue. If he took it without permission, then she might have a chance.

she could sue just as long as her ex boyfriend took the car without asking your daughter

Granting permission has nothing to do with liability. She obviously did not grant permission to wreck the car. If there is no insurance coverage she is certainly entitled to sue for her loss. If another car was involved she has a cause of action against that driver & their insurance company as well. Determine if any tickets were issued by the police as a matter of finding fault & then try small claims if the loss was under $5,000. That is the limit in small claims in many states, sometimes it is $3,000. If the loss was more u will have to have a more formal case heard in civil court. Again, there is nothing stopping u from prosecuting the suit yourself. Good luck.