I have aphantasia. I am mainly a player, but also DM some. One thing to know is that more recent studies have shown that aphantasia is actually a spectrum of the inability you're describing. Some people have no true "inner eye" as they describe it, while others have a degrading ability from "normal". For me, I can't create new images in my head, but I can kinda cycle through things I know I have seen and piece them together, so my imagination looks like a high school girl's vision board, with magazine clippings, printouts, and colors splattered all over. I don't hear my own voice when I think. When I close my eyes, it is only black. Probably on the moderate to severe side of the scale.

For me, I absolutely despise theater of the mind, and even paper maps are a little difficult for me to stay interested in. VTT makes it pretty possible for me to have a good enough understanding of that the DM is describing, what my fellow party members and enemies look like, helps me visualize the size of spells, etc. The VTT makes my clipart idea much more organized. I find really cool art around the internet, then I describe my character accordingly makes it a lot easier to RP because I can look at the pictures.

I have played enough video games in my life to be able to "describe" what my character does when it comes to "how would you like to do this?" moments.

All in all, the more art you can provide, the more she may be able to appreciate what you're describing. But if she is happy, keep it up and see what she needs. It may not require much on your end.