I’m very worried my brother‘s dog will not be able to handle our Chihuahua

My brother has a 250 pound English mastiff, I haven’t been around this dog too much, but I’m curious how similar his dog would be to mine? I have a toy Chihuahua who loves aggressive play. Will my brother’s dog be able to handle the Chihuahua? She can really be quite dominating in terms of strength and temperament when playing. 

For example when she has a rawhide in her mouth we know not to mess with her, and when she has a chew toy she absolutely obliterate it, throwing the toy across the room with stuffing everywhere. She really can hold her own, don’t even get me started when she plays tug, she gives it everything.