This is one of her challenged areas because she genuinely doesn't know how to commit to anything when it comes to "long term". That is why she tends to "need" so many partners and not be able to actually function in a consistent pattern. Somehow, your ex gained a sense of control by avoiding consistent "structure". Somehow, this is what she learned to practice in her history and this can also be due to having a condition called bipolar disorder where the individual experiences mania and then crashes and this makes it very hard for the individual to maintain a "normal" structure. However, this can also be borderline personality disorder that developed from an unpredictable childhood that was often chaotic and the only structure she knew was basically no structure that provided her with any sense of "consistency". Unfortunately, because she struggles with this challenge, she will create this instability in her children as well which is NOT fair or healthy for your's and her children.

At this point it sounds like she is "not" willing or receptive to getting help and seeing a therapist. So my suggestion is to approach this where you encourage her that by choosing to let you see to the children's needs it will free her up to having more time and freedom for herself without having the daily task of having to manage your children.