AYCE is for predictable support, for covered items. A new workstation is a change request, moves/adds/changes. Tell her the labor for installing a replacement is covered since workstations fail or are replaced on a fairly predictable cycle. However, new workstations are billed going in. After they go in, and after they've been added to the contract, then they are covered for additional support.

That's all support. You still put margin on sales. Sales are not covered in a support contract. If she doesn't like your margins, she can buy them from someone else. But that's effort on her part, and she doesn't want to do it; she wants you to do it, for free. Is your time free? Mine isn't.