Earlier quoted context omitted.
Indeed, the US tends to protect its criminals from justice, as long as they work for the government. It’s not callous, though, it’s just bullying. The “scapegoat” argument could make sense in a few countries without proper judicial system, but obviously doesn’t make sense with European countries.
The "scapegoat" argument makes sense here too. Mrs. Sacoolas was seen as a personification of Trump's foreign policy. People were calling for her head, for an crime that generally doesn't even receive jail time (in the UK or USA). People don't normally get incensed over non-DUI car accidents. People were out for blood because her husband and allegedly she worked for US intelligence agencies. If she was just a tourist…
The only reason for mentioning her being a spook is how she used that fact to escape.