I used to work in an art-adjacent field with a lot of people who had art degrees, and whether you have to be able to draw REALLY depends on what kind of work you want to do. The fact that stepdaughter is trying to get into graphic design (as opposed to fine arts) means she is taking the path of more realistic job prospects, whether she knows how to draw by hand or not.

But even if stepdaughter really can't hack it in her chosen field, the only thing LW will accomplish by telling her that is damaging their relationship with her. The husband is right, stepdaughter is at the age where she needs to be allowed to make her own mistakes, and "it didn't work out but at least my family encouraged me to try" is going to be a very different takeaway than "it didn't work out and my family's discouragement added insult to injury" or "I made it despite my family telling me I sucked and had no chance".