The first movie you're talking abt (the one with the bra designer) is Barbara Bel Geddes as Midge in "Vertigo". It's likely that you made the connection cuz James Stewart is part of the main cast of that one too!

The second movie is called "Rope" and is the 3rd (out of 4) Hitchcock movie James Stewart also stars in.

Glad to be of service. *Tips hat in a sassy way*. 😛