。
She can't swim.
Literal
She [topic-は] can't-swim.
A bare statement using 泳げない, the negative potential of 泳ぐ ('to swim'). 泳ぐ is a godan verb, so its potential is formed by replacing the final -u with -eru: 泳ぐ → 泳げる. The negative form is 泳げない. In Japan, swimming is part of the standard public-school P.E. curriculum from elementary through middle school, so being unable to swim is sometimes a marker of having missed those years or simply having an aversion to the pool — a slightly more remarked-upon fact than in many other countries.