Looking at a Tree she remarried 1948 so either Fred had died? (war years) or they divorced.
March 1948 Westminster 5c 985
Thornton, Patrick J. - spouse Wilcock or Hayward
Hayward, Phyllis I. - spouse Thornton
Wilcock, Phyllis I - spouse Thornton
GRO doesn't normally index a widowed bride under two (or more!) names. Suggests a divorce perhaps?

1947 electoral register has (as spelt)
Phyliss I. Wilcock at 29 Denbigh Street, Westminster (among others)
Not listed there 46 or 48.