The first one is silly but meant as a sort of compliment (though, probably meant to say 'you're not a striving career woman like me', from someone who feels the need to distinguish themselves form others in order to feel special).
The second is verging on being an accusation of incompetence and could well build into being just that. Be very, very careful, or you will find yourself missing promotion, getting a poor appraisal, even being performance-managed out of your job or being the one to be made redundant when cuts are needed.
Ask her each time what the issue is. Make her spell it out. Don't nod along or agree. Look as though you're taking it seriously. If she keeps doing it, you could even start taking notes.
Explain to her that you're really concerned about this repeated accusation of forgetfulness or confusion or disorganisation (or whatever it is) and want to understand whether there really is a competence issue, or whether perhaps it's just a bad habit she's fallen into.
You could, depending on the relationship, try using it yourself, about her, or colleagues in front of her, to highlight the subjectivity of her application of the term to you. So, ooh, Mummy brain eh?' when somone else slips up, 'oh no, maybe it's human brain, hmm?'.