I thought about that, and it's all the more ironic because her encounter with angels was only with Anna in *that* mode. I don't think Michael talked to her, did he? Anyway, I think since Michael was the one who erased her mind of that incident, then he was also the one who left her with a good memory/impression of an angel, and that he put it into her head that an angel is going to look after her children, Dean specifically. Maybe.