That's true - and that's why it's important to be accurate with the history. Amber Heard did not 'win in London' in the legal sense - but if others presume that's what it means when they hear it, and presume the US was a carbon copy retrial of the UK, then they will incorrectly make the wrong inferences.
Ironically, I don't think the UK case did her many favours at all - aside from being a defence witness for the successful side, it created an existing narrative from which Depp's team could begin to pull apart the truths/lies. It may have added to her discomfort - and many of the questions posed to her witnesses began 'in the UK you said....' - as form of picking holes in the testimony between what Amber Heard said on the stand and what the witnesses went on to say in their depositions.