。
She couldn't study abroad because of a lack of funds.
Literal
She [topic-は] funds-shortage [because of-で] study-abroad couldn't-do.
The particle で here marks the cause or reason — '(due to / on account of) X.' This causal で attaches to nouns describing conditions or circumstances (病気で休む 'be absent due to illness,' 雪で電車が止まる 'trains stop because of snow'), and is more compact than a fully-clausal ~から or ~ので. 資金不足 ('funds-shortage') is a typical Sino-Japanese compound noun built from 資金 ('funds') + 不足 ('shortage'), the kind of weighty noun that pairs well with this terse causal で. できなかった is the negative past of できる, the irregular potential of する.