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She spends a lot of money when she goes abroad.
Literal
She [topic-は] overseas [to-に] go [whenever-と] a-lot money [object-を] uses.
The conjunction と after a plain non-past verb expresses an automatic or habitual conditional: 'whenever X happens, Y happens.' This is distinct from ~たら or ~ば — ~と implies the consequence is essentially inevitable or characteristic, almost a law of nature. So 海外に行くと…使う = 'whenever she goes abroad, she ends up spending a lot.' The plain non-past 使う isn't 'is using right now' but a habitual present, fitting naturally with the conditional.