Who is responsible for paying medical bills

The questions is why is she only willing to pay 50%. We the 2 children playing together and things got a bit out-of-control?  Were both children tossing the tree limb?  Was the injury an accident or an intentional act? Frankly, if the other mother flat out refuses to pay 100%, then your only remaining option is to file a lawsuit.  You would then have to balance the cost of litigation against the amount of money you are seeking. While you may well be absolutely right as to what should be paid, the cost to collect may exceed what you can recover.  Are the girl's parents collectible if you get a judgment?  Do they have homeowners/renters insurance that might cover the bills? In my opinion, you need to sit down with an attorney to discuss the circumstances and your options -- including the cost.