Jcheney I am ignoring my needs for the moment, I just want to get a handle on how easy it would be to make her happiest with a very expensive purchase.
I think you should still focus on what machine will best suit your needs as most espresso machines include a steam wand which can be used to steam milk for hot chocolate. Of course this is usually a manual process and requires some skill/technique to get the best results.
I have an ACS Minima which has a 2.3L steam boiler. With such a large boiler it takes around 8-9 minutes to reach temperature. So it depends on how quickly you need access to steam from initial onset of craving 😄
I know that Quickmill DB machines allow you to independently toggle the brew and steam boiler. Not sure if they are available in the U.K. or where you are based.
If you want something more automated a sage bambino plus will steam milk itself to a good standard and will be ready to steam in a few seconds from switching on the machine. Sage machines have reliability and repairability concerns though.
@DavecUK is it ok/safe to add chocolate to milk pitcher, melt, add milk and steam together? This will usually give the best result as the milk is fully incorporated with the chocolate.