SIL ruined my thanksgiving announcement

Showed up to thanksgiving at my in laws ready to announce the good news to his family when his brother informed us that my SIL was making bets on when I'd get knocked up (married since August 2nd)

It ruined our day and we didn't announce it. We found out she was making the bet with her 2 sons (16&13), her brother and his wife (they told us and confronted her ) and 2 family friends that we know of.

It hurts so badly, because we were already having a hard time telling his parents because they always loudly voiced their opinion that they want us to wait until we're married at least 5 years and that I have a better paying job. I understand their concern, but it wasn't exactly planned, but also we weren't preventing it, letting whatever happen happen.

My SIL has 2 kids, 1st when she was 16 (gave birth at 17), 4 divorces under her belt and married(and divorced) her 2nd child's dad.

My husband and I are at a loss for words, we're so upset with her and now she'll rub it in our faces if we announce anytime soon that we are pregnant.

Any advice or words of encouragement would be appreciated.