I would say it is unusual not to have January exams in most subjects, especially those that are not predominantly coursework.
My DS is in his final year, after a YII last year - he has always had January exams, as have most of his school friends (some of whom have now graduated) and other people (Relatives and friends DC) we know at uni. Whilst he is quite social, socialising is the last thing on his mind at moment - and his friends also doing final year - as these exams count towards degree grades, and there’s no such thing as re sits in final year!
Whilst first year results don’t count in final degree, they do usually have to pass all exams, and re-take any failed ones in the summer re-sit period, whether from January or summer. First yr results are also taken into consideration if they apply for a YII, or an internship, or an optional year/semester abroad. DS had friends who missed out on the latter due to poor marks in 1st year winter exams.
So, whilst your DD is lucky if she hasn’t got January exams, Benji, her friends who probably DO have exams are definitely doing the right thing by studying and not going out.