。
It's just a short walk.
Literal
Walk-and immediately is-よ (polite).
すぐ ('immediately, right away, nearby') is a remarkably compact adverb — in spatial contexts it means 'right near,' in temporal contexts 'right away.' 歩いてすぐ ('walk-and-immediately') is an idiomatic fragment for 'a short walk away.' The よ asserts the information reassuringly.