。
She has 1000 yen at most.
Literal
She [topic-は] much-even 1000-yen-only is-not-having.
Two patterns. 多くても is a parallel to 多く見ても ('at most'), built from the te-form of 多い + も — 'even (at the) most.' しか~ない is the restrictive 'only X / nothing but X' pattern: しか attaches to a noun and forces a negative predicate, with the meaning 'only that thing (and nothing else).' Compare だけ ('just X') which works with affirmatives. Here しか持っていない = 'has only.'