I'm sure all ladies shoes are manufactured in a similar fashion. Your shoes may be slightly different in construction and may require a different method than the ones shown here for modification.
I started by removing the small plastic heel cap with pliers, then bisected the decorative leather sole at the heel and removed the sole portion that was glued to the heel. Making sure not to damage the heel veneer, the white heel covering was peeled back and removed. Set aside this scrap for later as we'll be using it in Step 6 to cover the underside of the shoe where the old heel used to be.
The heel of these shoes were held on with a large industrial cleat that mechanically fastened the heel to the sole and adhesive. The cleat was attached from the top of the shoe under the insole through the sole and embedded deep in the plastic heel. It was no small undertaking removing this cleat. I worked for about 20 minutes getting these heels off.
Once removed the old plastic heels can be discarded....
After the cleat and heel are removed it's time to prepare the shoe for welding.
This shoe has a steel shank under the insole for support, my shoe had the shank riveted to the insole, so the entire insole was removed from the shoe. The underside of the shank was abraded at the heel with a rotary tool, this will clear away any debris and prepare the surface for accepting a weld.
The heel cleat opening left a jagged edge which needed to be fixed. I easily cut away excess shoe around the cleat opening and then reinserted the shank-insole back into the shoe to approximated where I was going to weld my new steel heel spike, the new heel location was marked on the steel shank with indelible marker.