Main tasks are: UX design and app prototyping in Adobe XD and Figma. Tons of research with an average of 30 Safari tabs open. Rendering of jewellery models in Rhino 3D. She also uses other professional & personal applications, like Photoshop, Lightroom, Miro, Notion, Slack, ...at least 20 apps are open normally.
Her current RAM usage can easily reach 100GB, so I won't be recommending 16GB to her, which is the maximum M1 Mac Mini can have. 64GB will be the minimum we'll be comfortable with.
But you are right, there is a case for the Mac Mini here, however the top spec Mac Mini Pro costs similarly to the Mac Studio Max.
LG display - very low chance she will go for it. The cost saving of $1,000 for her won't be worth looking at black plastic bezels for 10 years. I have nothing against this, but she is a hardcore Apple design fan and is almost certain to go for the Apple Studio Display.