Isn't that what the makeup people are for.
Hugh Jsckman's the pretty boy type but he could still do the ugly double in The Prestige. Salma Hayek is one of sexiest women i've ever seen, more so some years back, and she still could play the ugly vampiress. I could go on and on, but you get the point.
If the man's trying to be kind and avoiding to mention that she's not talented enough for the role, then fair play. Nothing so bad about a white lie. Although, as mentioned before, the actress who's cast must feel great about herself.