My husband and I have friends that are an engaged couple. We’re close with him, and not very close with her. She’s extremely petty and just not the type of girl we want to hang around for extended periods of time. He tried to propose to her in December, but she literally walked away from him every time he got on one knee, because he was doing it at a Christmas light event and she “hates Christmas lights.” They ended up getting engaged this past February. Within two weeks of getting engaged, she took her ring to the jewelry store she works at and exchanged the middle stone for a larger one without telling him. She literally went from a 1.42ct to a 1.5, so it’s not noticeable at all. He still doesn’t know about it. Now, she’s told some mutual friends and I that she’s already purchased her wedding band to go with her ring. But she’s paid over $9k on this band, but isn’t planning on telling him she’s bought it until closer to their wedding in the late fall of 2021. That way, she can pay down the total for over a year and she’ll tell him the “adjusted” price of whatever she still owes on the ring. He just recently got a new (used) car and is the only one contributing to their savings account. I don’t feel like their financials are any of my business, but knowing that she’s lying to him really irks me because this isn’t the first time she’s done something like this. I’ve tried encouraging her to be upfront and honest with him, but she brushed me off. I know if I was in his position, I would want someone to tell me. But it feels weird because it’s a conversation about finances and therefore doesn’t feel like my business. So what do you guys think? Is it worth telling him?

To add: these two examples are not the only thing she’s lied to him about, especially when it comes to the full cost of material things. These are just the most recent and therefore the ones at the forefront of my mind. I’d love some perspectives from men and women.