S/o was a social media manager working as a freelancer and her client just laid her off without a 2 weeks notice. Now they want to take her design templates saying it’s their property.

Hello everyone, longtime lurker here. I felt like this was the right place to ask about this. Does my partner have the right to keep the designs she did for her client working as a freelancer? For further context, the client always gave delayed payments, failed to provide a 2 weeks notice before contract termination, and is unwilling to pay for the work hours she rendered for the first week of the year, but is audacious enough to demand that her templates are their property. Any insightful answer would be highly appreciated!