。
She was more beautiful back then than she is now.
Literal
She [topic-は] those days [now-than-より] was-more-beautiful.
より is the comparative particle, attaching to the standard of comparison (the thing being compared *against*). Word order in Japanese comparison is fluid: A は B より adjective. Here 'now' is the standard and 'those days' is the topic — the implicit shape is 'as for those days, [she was] more-beautiful-than-now'. そのころ ('around that time, those days') is more atmospheric than crisp その時 ('at that time'); ころ vaguely covers a period rather than pinpointing a moment. The bare comparative without も (より rather than よりも) keeps the sentence quietly understated.