The meaning of Mother of the believers

بسم الله الرحمن الرحيم
In the name of Allah, Most Gracious, Most Merciful

The title "mothers of the believers" doesn't immunize the wives from deviating. Even in the case of ones own birth mother, if she deviated away from the path and started transgressing and doing wrong Islam requires us to unconditionally distance ourselves from them.

Quran (11:113)
"And incline not toward those who do wrong lest the Fire touch you..."

But when it comes to the wives of the prophet and their being mothers of the believers, this is not motherhood in the truest sense of the word.
Because some aspects of motherhood apply to them while others don't.

For example,

• we can not marry our birth mother's daughters/sons, but the believers can marry the prophet's wives offspring.
• Our birth mother doesn't have to wear hijab in front of us as she is our Mahram, but the prophets pbuh wives are required to wear hijab in the presence of the believers.
• We can inherit from our birth mother but the believers do not inherit from the wives of the prophet.

Therefore the only other aspect of motherhood that applies to both birth mothersand wives of the prophet alike is marriage, in that we can not marry our birth mothers and likewise the believers can not marry the wives of the prophet because they are like our mothers in this respect.

Allah (swt) revealed in the Quran the possibility of apostating being Muslim and has warned us against it.

Quran (3:144)
"Muhammad is but a messenger, messengers (the like of whom) have passed away before him. Will it be that, when he dieth or is slain, ye will turn back on your heels? He who turneth back doth no hurt to Allah, and Allah will reward the thankful."

The above warning does was meant for the muslims of that time, wives and companions included. Also lets consider the following chapters in the Quran Surah 33 where Aisha was called mother of believers is said to have been revealed in year 5AH. Surah 66 where Aisha was criticized and threatened is said to have been revealed in year 7-8AH that's 3-4 years before the prophet passed away and 2-3 years after she was called mother of believers.

Quran (33:6)
"The Prophet is closer to the believers than their selves, and his wives are their mothers..."

(Quran 66:4-5)
If ye twain turn unto Allah repentant, (ye have cause to do so) for your hearts desired (the ban); and if ye aid one another against him (Muhammad) then lo! Allah, even He, is his protecting Friend, and Gabriel and the righteous among the believers; and furthermore the angels are his helpers

It may happen that his Lord, if he divorce you, will give him in your stead wives better than you, submissive (to Allah), believing, pious, penitent, inclined to fasting, widows and maids.

The verse about the wives being mothers of believers was revealed around 5AH, Yet 2-3 years later Allah criticized her for plotting against the prophet, this further proves that being a mother of believers does not protect the wives from deviating. That is because despite the fact she was honored with the title of mother, she still plotted against the prophet.