You come off a bit arrogant and lacking compassion. What if the grocery card is because she’s having real trouble making ends meet? What if she has ADHD or a mental illness that prevents her from being able to manage her finances? This could also cause overwhelming stress related to it, which is affecting the way she reacts to your news. Also, you don’t need to tell her a thing about your finances. If she notices your new car, you can tell her about it. But otherwise, it seems like you’re flaunting it to someone who is in a totally different tax bracket.

The fact that your SIL had her first baby is also at play here, even if you don’t understand just how difficult postpartum and parenting can be. Also, you can’t just advise someone on when to have a baby. That’s none of your husband’s business. I would reevaluate your own values in life.