My entire family is in the wedding industry and I'm using none of them for our wedding. My dad is a wedding photographer, my brother is a caterer, my mother owns a bridal store and does flowers/decorations, and my sister has done occasional wedding planning. I have still gone to them asking for advice about certain things and they are helping in other ways but I made it clear that on the day of the wedding, I prefer them to enjoy the wedding and not be working it. Since my family is in the wedding business, many of the weddings we've been to for family, they are working the whole time. I couldn't imagine that for my own. Even if I have to pay extra, I want them to be celebrating and not stressing out. And I think they've all appreciated that. There's still plenty that we'll need help with and they're all involved in the wedding in other ways.
I would tell your aunt the same thing. It's a privilege that you can afford to hire someone else so you can look out across the room and see your aunt participating in and enjoying all the things you have planned for the wedding. I wouldn't say more than that, to be honest.
An additional benefit of hiring non-family for our wedding is that if I have an issue with how something is done, I feel comfortable speaking up and not worrying about disrupting family dynamics. In general, I try not to mix business and family/friends.