Not true. They don't need to hear them, they need to feel them.
No artist needs a fair weather friend, an employee or customer or partner who waits to do the calculus before deciding if they're going to be there for them.
No, if you want her to go all in, if you want her to take the risk and brave the fear, then it sure helps if you're there too, no matter what. There's a cost to that, a pain and risk that comes from that sort of trust. After all, it might not work. Failure (or worse! embarrassment) might ensue. That's precisely why it's worth so much. Because it's difficult and scarce.
Later, when it's all good and it's all working, your offer of support means very little. The artist never forgets the few who came through when it really mattered.
Who's got your back? More important, whose back do you have?