<p>Off the top of my head:
Bryn Mawr/Haverford/Swarthmore/Penn
Mount Holyoke/Smith/Amherst/UMass-Amherst
Agnes Scott*/Emory/Georgia Tech/Georgia State/Spelman/U of Georgia</p>
<p>Rules for cross registration vary. The two main obstactles are calendars (when school starts, stops for break, resumes, etc) and, #1, distance/access.
*you’d most definitively get good merit aid there but the math offerings would definitively need to be supplemented by math offerings elsewhere</p>