Where does she get the money? If it from credit cards, cancel them. Keep one in your name and your name only and don't gell her you have it. Don't give her any cash. Have the older kids do the household shopping. If you have a joint checking account, change it to one in your name only. Hide your checks - if she is desperate she may forge your signature.
That should control the financial problem. With her funds cut off she may be more amenable to counseling. And then again, she may not.
Shopping can be her drug of choice that gives her momentary calm, or a high. But then this wears off and her old feelings return. She needs to get her fix again with shopping for her next high. It is like being a heroin addict. You get a fix and get high, only to come off the heroin and need another fix to get high again. It can be an addiction to shopping. Her situation is serious! You will have to take total control over your finances and close all of her credit activities and put a freeze in her credit reports so she cannot open another account. She can have access to a set amount of money to spend as she wishes, but this would be all she is allowed to have a week or a month. She is not to have access to checking and savings accounts. You will have to be the one to grocery shop and make other important purchases. She will really protest and threaten you because this will mean going through withdrawl and this is going to be painful for her. If she is willing, she needs psych help.
I agree with Jo. Many people like to shop and get a bit of a rush from it. Some crave that rush to the point of jeapardizing their whole family. That sounds like the situation here as you know. Using shopping as an escape mechanism is can be part of her mania when her bipolar is uncontrolled. As you said, she could do it during her depressive episodes as well. Or shopping out of control like this (and shopping way beyond her means is out of control behavior) can be an addiction in itself. So, somehow if you can get her to take her illness seriously, that would certainly help tremendously if it won't solve the problem completely. You could present it in a different light than what it is doing to you, the kids and the finances and talk about what it is doing to her. The reason why I'm afraid it is part of her mania is because she is so resistent to stopping. Mania feels really good (believe it or not) but depression doesn't. That's the uncontrolled cycle of bipolar. So I would focas on when she doesn't feel good. How if she goes to a psychiatrist and takes the proper medication---- she can feel even and balanced most of the time. She won't feel as exhausted (as cycling in bipolar is exhausting). Talk about how medication will make her feel better and make it all about her (even though we know it isn't all about her---- she's hurting everyone right now).
While you are working on that----- take some steps to protect yourself. Start an envelope system. Give her an envelope for "gas" money, "food" money and lastly, one for "blow" money. That is the amt of cash she can spend every month on whatever. Then get the credit cards away from her. Then she can feel like she can spend but it is within what you have. She may screw up and spend that food money before the end of the week or month or however you set it up (I'd do weekly at first)---- but that is better than finding 10,000 bucks on a credit card. She may not like it---- but if she thinks she will have some ability to shop, she may not have the usual tantrum. I'd also consider seeing a lawyer and if you have any assets either move them into just your name or set up a trust (which you could do under the pretense of the kids).
Lastly, some people refuse to ever help themselves. If you've given a valient effort to get her medical conditions under control and she still refuses--- Build your case for seperating. Document things like her credit card spending to date and whatever else you think would be relevent to gaining custody of your kids (her refusal to treat her mental illness . . . good one to document) and do it. That is hard but at some point you have to think about the damage she is doing to the kids. They live with her and heaven forbid they see her behavior as normal. It could impact their adult life very negatively. Good luck. That is sure a difficult situation and you seem like a very patient man.
It sounds like you have let her have her way to long and your first mistake was letting her have credit cards you should take over paying the bills take away her credit card and if she has a tantrum let her have it, if you cant get her to go for help on her own if she is really mentally ill you can get a court order it sounds like she just has a spending problem and if she does not have the money she cant spend it, now can she? but if the consling did not help and she wont take her meds for bi polar there may not be anything you can do but divorce, but can you not get some proof that she gets out of control and has these tantrums and spending habits she really knows what she is doing and she knows that you will put up with it, in other words she has you by the short hairs, i have seen this many time they use their condition to control if they can i wish that i could give you some help and hope, but i do wish you luck, for your sanitys sake you may have to divorce i think the children are old enough to understand things luck jo