ΔE 29.4, loose: different enough that you should pick on purpose. Fairy Skin is a little lighter, much more muted, cooler than Rust.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 29). Fairy Skin is a little lighter, much more muted, cooler than Rust.
The same difference applies the other way round: Rust is a little darker, much more saturated, warmer.
ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.
See Rust on the colour wheel See Fairy Skin on the colour wheel
All matches: Rust equivalents · Fairy Skin equivalents