<human>: Is it possible to teach an adult dog to read dog body language? 

We are currently fostering a female 3 year old staffy/lab lab mix with our resident 4 year old male pit/ACD mix. Their first meeting went ok, we did a side by side walk and after about 2 hours they were wrestling and playing together. Fast forward a few days and our resident dog has hurt his ankle (nothing unusual, speed of an ACD handling of a pit causes a few rolled ankles) and is a little crabby. Add to the mix mini-dachshund on create rest for DDD and you've got our house of the weekend. 

Now, our foster has been very good at play, tolerating our resident dogs wrestling and very cuddly. BUT she is not heeding either hurt dogs' "leave me alone" posturing (head turned, low growls, fur up, ect) and she has been snapped at by the dachshund and got into two tussles with resident dog. 

Luckily my resident dog does give warning but since the foster isn't responding, we have been either trying to call her over and distract her or telling him to let her get close, which I don't really like doing. My husband is of the mind to let them sort it out since the fights have be LOUD but not violent. He thinks the resident dog will teach the foster that a face turn will result in a snap of you don't leave him alone. I would like to find a solution to help her learn to leave him (and the dachshund) alone when asked.

Condense the text into a few key points
<bot>: new foster and resident dog are friends except when resident dog asks to be left alone. Foster doesn't seem to read doggy body language and fights have broken out.