I thought I read somewhere that she must come to the Uk within 60 days of the visa being issued. Is that correct ?
The vignette (visa) will have a valid from and a valid to dates on it you must travel within that timeframe.
Think you are confusing the fiance and spiuse visa's Fiance visa has a duration of six months and a start and finish date. Need to travel after start date, get married and submit a spouse visa application before the end date on fiance visa. Spouse visa from outside uk had a 30 day window which was increased to 90 days during covid and think still at that duration. Again a start date and had to travel to UK to pick up BRP within that 30/90 day window.