[Help] I think my dog may be injuring her dog friend's ears when they wrestle. How can I train her out of this?

My dog is 1 year old, and she has known this dog (Same breed, male, also 1 year old) since she was about 3 months old. We're good friends with his owners so they probably meet up a few times a week and wrestle when we hang out.Neither of them ever yelps, and they basically become a tumbleweed for an hour or so, until they get exhausted and lay on the ground 'complaining' at each other (it's a very talkative breed).However, my friend's dog has had scabbing on the tips of his ears, and at first they thought it was their cat, but then we saw my dog going for the ears. They're never visibly bleeding, but I think she may be scratching them up. The only thing is, I'm the only one that seems concerned. I've brought it up to the owners, suggesting maybe we should watch them and try to keep her from doing it and see if we can get her to stop, or we tape up his ears while he's over to allow them to heal, because maybe old scratches are being reopened when they play. They just shrugged it off and said it was 'no big deal'.But I'm super uncomfortable with my dog doing this to theirs, and I don't want it to continue. What is an easy way I can train her out of it? Do I just need to watch and intercept every time she goes for the tips of his ears? Should I avoid having them play together until it's healed? Usually the other owners are the ones that bring him over, or initiate a playdate.Help! via /r/dogs http://ift.tt/2rEYk5u