Yeah, I agree that's not okay either. You have a right to put your hard-earned funds towards that; she is not entitled to your money in the context of you financially supporting the baby. I'd just be wary of kicking her out just so you don't have to look at her being pregnant, if you see what I mean, but the financial thing is another issue.

The issue you have is with your husband, then. You need to sit down with him and establish: 1) money is definitely getting saved and put towards IVF and 2) if after 1) you still have the capacity to help SIL out in either way, then you'll do it only insofar as it doesn't take away from the IVF fund.

The unfortunate issue is I think your husband sees himself as a "foster parent" to her baby already, which he can easily, unlike you, because he conveniently is related to the baby by blood, unlike you, and you need to make it clear to him that you're not satisfied with that option for parenting personally, and your savings going or not going towards IVF is a dealbreaker. This may end up causing marriage problems between you, but yeah, I do believe you have a right to put your money towards IVF if that's ultimately a significant life goal for you.