walaikum assalaam
Shaykh ‘Abd al-‘Azeez ibn Baaz (may Allaah have mercy on him) was asked:
Some women braid their hair and when they do ghusl following janaabah they do not undo their braids. Is their ghusl valid? Please note that the water does not reach all the roots of their hair. Please advise us, may Allaah reward you with good.
He replied:
If a woman pours water over her head, that is sufficient, because Umm Salamah (may Allaah be pleased with her) asked the Prophet (peace and blessings of Allaah be upon him) about that. She said: I am a woman with braided hair; should I undo it when doing ghusl for janaabah? He said: “No, rather it will be sufficient for you to pour three handfuls of water on your head, then pour water over yourself and you will be purified.” Narrated by Imam Muslim in his Saheeh.
So if a woman pours water on her head three times, that will be sufficient and she does not need to undo the braids, because of this saheeh hadeeth.
https://islamqa.info/en/40329