My friend's DP has teens and an Ex, and she is quite critical and sneery of the Ex not working or only working a small number of hours. Probably because she has worked very hard to have a good career. It does end up sounding like trying to be the better partner or wife, comparing oneself to the ex.
I think it grossly unfair to be so judgemental about a woman who is the resident parent to the two teenagers that her P walked out on. Who perhaps choose with the Ex that she would look after the children and sacrificed her career/job prospects to do so. Added to that she has had her husband leave her (possibly for an OW, my friend has never been clear on that) and is going through a divorce. I reckon is not unreasonable for her to be taking a while to build a new life for herself.
Now, the case with your DP might be totally different. Maybe he is a much more involved father and the split was amicable/her choice. But its bound to take time for her to build up her business and may be putting more hours in than she's getting money to show for it. (Privately, I reckon managing to make £2000/year selling small quantities of water with unproven medical benefits is a little impressive in an odd way).
Also if she previously wasn't working, of course she'll feel busier now that she is. Just because she isn't wildly successful doesn't mean she isn't working hard.
I might be taking umbridge at your comments because I am a SAHM with ideas about small ways to become self-employed and earn a bit of money which I would hope to increase my number of hours doing as my child/ren get older. If I had already started I'd consider myself a WAHM, even though I might not earn as much as other WAHMs.
I can see that your DP might value your career minded outlook if it is different from his ex. But try not to get involved in judging her, and if he does openly, I'd maybe start wondering what he'd say to his next GF if/when he moves on from you - oh she was so career/money focused she never had time for me... etc.