Cadsuane referred or hinted at that backstory several timed, even obliquely in New Spring when she confronts the newly raised Moiraine.

Shortly after she gained the shawl herself and thought herself unstoppable, Cadsuane got herself involved with a toothless (ie: extremely old) wilder in the Black Hills whom she referred in a later scene by her name, Norla. We don't know exactly what happened between them. What we know is that in her time with Norla, Cadsuane ended up gaining one by one the ter'angreal in her paralis net.

IMHO, from the way she mocks young Moiraine's arrogance and delusion about her power in New Spring, what happened to Cadsuane is something like this:

She always had an "adventurous" streak which at a young age was probably much tainted with recklessness and arrogance, and she was the strongest channeller of her time, and she's headstrong and cares not much for authority. She must have been a complete pest as novice, and once raised she was probably uncontrollable, listening to no sister and leaving the Tower for "adventures" so people with authority over her (eg: Green Ajah head) couldn't stop her from doing as she wished. Much like Moiraine - or even Rand mid-series, but perhaps worse at least than Moiraine. What people call her "arrogance" today was probably nothing next to how she was as a newly raised sister.

One day she found herself in a village in the Black Hills, where a toothless old woman named Norla was the local wisdom, and was a wilder, and in this isolated area, perhaps Norla wasn't very discreet about her ability, and the villagers perhaps feared her a bit... but like Nynaeve bitching about her doesn't mean if a stranger threatens/criticized their Wisdom, they wouldn't fall like one behind her....

Puffed-up newly raised Cadsuane, all proud of her shawl, thinking herself the strongest woman ever and totally unstoppable, took upon herself to teach that old arrogant wilder a lesson that using the Power was for Aes Sedai and Aes Sedai alone. Then she hit a wall, because Norla had this paralis net and Cadsuane's strength was nothing to her, her channelling couldn't touch her, and the villagers all fell behind Norla to stop that arrogant Aes Sedai who thought to tell them what they should do in their own village. Cadsuane probably made threats about the wrath of the Tower and Norla anf the villagers captured her (so she didn't fled to the WT and brought back sisters) and Norla began to teach her about wisdom and authority, that wielding authority wasn't about a title and her strength in the OP to bully everyone into doing what she wanted, that even an old frail toothless woman could defeat her, and kill her if she wished. She shaped Cadsuane into the formidable woman she became - shaped her into a leader, and when she was satisfied with her "growing up", she let her go. Basically, she's "retrained" her. Norla was probably quite near the end of her life when she met Cadsuane, and each time her "pupil" progressed to her satisfaction, she gave her one ter'angreal from her net, until at the end Cadsuane had them all.

Cadsuane seems to remember her time with Norla (that of course she never revealed to anyone... much too humiliating!) lately, because what she went through isn't so unlike to how she was attempting to deal with Rand... or Semirhage for that matter. She might have been in a position similar to Semirhage in that village, for a while...

I think it's likely we get more details about this backstory soon, because it seems to me Cadsuane has forgotten some of Norla's lessons and paid for this by her failure with Rand. Cadsuane with Rand was perhaps getting a little too much like young reckless Cadsuane, a bit too careless about dangers (Semirhage, the male a'dam, the CK), a bit too prone to take decisions that aren't hers to make, too confident in her power. I think it's likely Cadsuane will give more details about her time with Norla, and realises what she forgot and what she did wrong with Rand. I think Rand back from Dragonmount will reconcile with Cadsuane (he will come to value her the way he valued Moiraine post Rhuidean, I think), and I don't think the apologies will be one-sided. I think Cadsuane will tell Rand she was all too much like him as a young woman, and how Norla dealt with that arrogance and recklessness, and how she thought to shape him into someone formidable and "grown-ups" the same way, and what she forgot/didn't did right that made Norla succeed but her fail... Rand might answer perhaps she didn't fail, and tell her some of what happened on DM.