hehe :-)
I'm guessing that in this context a 'semi' is a British colloquialism for a type of dwelling, perhaps something like a duplex.
But of course the larger question is, if she demanded a fullsize American-style semi truck and trailer rig as pictured , ostensibly as a requirement in order to run her business would the Government refuse? It's a head-scratcher for sure.....
semi = semi-detached.