WIBTBF If I gave my SIL financial advice

Throwaway and I'm praying she doesn't see this. So my SIL has come into around $10k thanks to a lawsuit (after fees and all that). When I asked her what she was going to do with all that dang cash, she gave me her game plan and stressed that she wanted to put money away. However, she's been spending a ton of that on new things for herself--I'd peg a grand in a week. And she still has plans to spend more of it. Cool, treat yourself—but here’s where things get tricky: She has not had a job in years, my BIL supports them both. He pays for the mortgage, the bills, and has bought her a car. My husband's family has previously really disliked her for other reasons, but the biggest being that they think she just “wants to be taken care of” and are concerned that BIL will be taken advantage of. They’ve had several “heart to hearts” with him, but the two are still together. The past few months have been really smooth and everyone’s gotten along really well, but my husband and I know that they’d probably go right back to hating her if they found out that she isn't using at least some of this money to help BIL with finances. I really like my SIL and would hate to see the relationship with our in-laws be strained. So, WIBTA if I gently suggested she save some of the money and not impulse buy so much? And if anyone has any ideas for how to approach her on this that would be super.