Is my 18 week old female puppy ok to be left playing with a 19 week old male and 10 month old male?

i have an 18 week old alaskan malamute and my sisters have an 19 week collie and a 10 month old large mixed breed they play well together but lately the large male mixed breed keeps trying to mount my female, they normally play outside so im scared that he could do her damage if i dont keep my eye on them constantly but the 19 week collie male has no interest atall in trying to mount her i might sound daft but have only ever had male dogs before lol x thanks x