Who is the beautiful girl on fathers TV in 1949 film The House of Tomorrow by Tex Avery?

You're likely referring to the animated short "The House of Tomorrow" (1951), not "The House of Tomorrow" (1949) - there's no such Tex Avery film from 1949.

In the 1951 short, the girl on the television is a generic, idealized female figure. She is not a specific character with a name or backstory.

Tex Avery's cartoons were often filled with beautiful women, but they were typically exaggerated and comedic, rather than realistic portrayals.