If you are married to a higher earner, it's absolutely easier to pursue your own career.
A business is only viable, if its financially viable. Ops is not.
And quite frankly, its not true that you can't do a high earning job unless you have a sahp at home. I have one and was a single parent. All my female peers at work manage to have a high paying high responsibility job and their husbands are not sahp.
If one is a high earner the other is a sahp or works very pt or remains in a low paying job for flexibility, its because they have both chosen to. Its a choice, especially if the other is a high earner.
When you are self employed, you have to accept at some point, it's not financially viable. If her dh needs to pay her tax bill, it's not viable. That's why she needs to look at changing her job.
And let's be honest, if there's very little Income coming from someone's job, there's very little point in doing in.
Women are at a disadvantage in the work place. It doesn't mean they have to withdraw, especially if their husband earns well because childcare is easier to afford.