How do I handle a dog that is being aggressive towards mine?

Hey everyone.

I am currently dog sitting a 2 year old female pitbull mix that looks like she recently had a litter and her owner said she was also fixed recently. I have a year and a half male pitbull mix who is such a sweetheart and has never hurt or even gone after another animal or person. He has always been patient with dogs that show small signs of aggression and will just walk away from any situation that seems off to him. I did not have time to schedule a meet and greet because the owner requested me the day of (I probably shouldnt have booked it without a meet and greet so thats on me) but she assured me that she was well-behaved, friendly with other dogs and other people. I always let a new dog roam around my apartment before introducing them to mine so they feel a bit more comfortable about where they are. When we introduced both dogs with us there, the owner was hesitant about them interacting which seemed a little weird because my dog just wanted to say hi. I assumed she was hesitant because he usually gets excited when he meets a new dog but calms down a few minutes later. Her dog did not play well at all with him and sounded very aggressive but she said she "plays rough." I've had dogs that played rough in the past so I trusted her word and then she left. Throughout her stay she has progressively played more rough/aggressively with my dog and my dog has been patient thus far like he has been in the past, but we have never had a dog that behaved this way.

She has snapped at him for bones, randomly jumps on him and sounds aggressive when they are playing, attacked him for sniffing an empty food bowl when they weren't even eating (I've had him locked up and her loose during meal times), goes after him if we pay any attention to him over her at all. I've never experienced this with any dog before and was hoping to get advice from those who have experienced this because I can tell my dog has become agitated and this is very unlike his personality. I wish the owner was more open about her having these behaviors but she may also not know that she behaves this way towards some dogs. Also, any advice on how to approach this with owners?

Thanks in advance