Trying not to go against bio mom but disagree with what she told my step som

My step son has nice teeth. They just aren't super straight but I think they're cute. He's 18 and recently got braces. His mom has been telling him his teeth are never going to look good and pushing him to get veneers. I know she's their mom but she would put them down a lot. So now he's planning on getting the braces off and just getting veneers. But he just needs to be patient. There is no reason to get veneers when his teeth are perfectly fine. They just aren't really straight. Which is what the braces are there to fix. Plus he's so young. I don't want to go against his mom but I don't think he should get veneers just because his mom said his teeth will never look good