Honestly I don't see this as shade. She probably just saw the pic, thought it was cute, and wanted to let everyone know about it. I don't even think she holds that much of a bitterness towards Gaga, because Gaga doesn't care much from her end about any supposed 'feud', it's media-manufactured.
Probably wasn't the most tactile way of doing it, but I've come to expect that of Madonna. It's how she is as a person.