Latex is a superior product to anything else used to upholster a mattress.
Your pillowtop is filled with polyurethane foam and likely has some memory foam.
If you bought the plush pillowtop, the gauge of wire is thinner too.
The Blisswood has changed names. The newer model is the Heidi. There's no need to second guess the recommendation. For the firm support you need and the comfort she wants, the soft latex topper is the one to get with a Heidi Luxury Firm mattress.
Here are links to both, the mattress and topper.