She was determined to go abroad, but her father told her not to.

Literal

She [topic-は] no-matter-what foreign-country [toward-へ] go [quotative-と] said [but-が], father [topic-は] don't-go [quotative-と] said.

Two contrasting quotes joined with the clause-final が ('but'): she insists 行く ('I'm going') and the father issues 行くな ('don't go'). 行くな is the prohibitive form of 行く, formed by attaching な directly to the dictionary form — a blunt, masculine command typically heard from authority figures (parents, coaches, military). It's the natural 'don't!' form for 行く ('go'), 食べる ('eat'), 言う ('say'), and so on. へ rather than に on 外国 emphasizes the directional thrust of going there. Together: a generational standoff in classic shape.