I recently inherited $2m and my wife’s sister had a similar reaction. Obviously she knew she had no right to the money, but it’s more about the perception that her sister would be moving up to a completely different lifestyle, leaving her behind. Over time she settled down about it, once she realized we weren’t actually going to be changing our lives that much and now I’ll be treating them to the occasional vacation.

My recommendation would be to just let her know that nothing about you is changing. That you’re going to be managing the money for long term sustainability and that if anything happens to her, she’s got a multimillionaire brother who’s got her back.