Spot this kinda thing constantly. It's like people downplay someone's skills until they need help, then suddenly they're the expert. Exactly what @nathan776 is pointing out. Happens at work, with friends, even in families. Someone gets mocked for knowing how to fix stuff, but who gets called when the wifi drops? Makes you realize how often we take practical people for granted.
Maxcampbell nailed it with the downplayed skills thing. This pattern shows up everywhere, from home repairs to tech support. People get sidelined until their knowledge saves the day. Your sister mastering brewing is a classic case of becoming the unexpected expert. It's a shame we only see how good someone is when things go wrong.