My Minerva's Emporium page used to tell you where she is. It now also tells you what she's selling: this visit's plan list and the next one, with bullion prices at her 25% discount.

She works through 24 numbered sale lists, one per visit, and every fourth is a Big Sale that sells everything from the three lists before it. Next up is List 3 at Fort Atlas (Sep 28–30, 12 plans, including Chinese Stealth Armor, Chicken Coop, and the T-65 Stealth Boy), then the List 4 Big Sale at Whitespring Resort (Oct 8–12, 42 plans).

The lists are cross-checked across the Fallout Wiki, falloutbuilds.com, and Nuka Knights. Where I could only find a price in one place, the page shows a dash instead of a guess.

See it on the Pip-Boy page (Minerva's Emporium): https://fallout76er.com/#section=resources&page=minerva