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While drinking coffee, she had a pleasant chat with a friend about the football game.
Literal
She [topic-は] coffee [object-を] drink-while football [of-の] match [about-について] friend [with-と] pleasantly-chatted.
Three grammar pieces stacked together. ~ながら ('while doing') joins two simultaneous actions performed by the same subject. ~について ('about, concerning') marks the topic of conversation. と marks the partner of a reciprocal verb (歓談 — see below). 歓談 is a written-leaning two-kanji word, 歓 ('joy') + 談 ('talk'), meaning 'pleasant, congenial conversation' — a small upgrade in formality compared to the everyday おしゃべり or 話す. フットボール is rarely heard in Japan as a sport name itself — Japan typically calls 'soccer' サッカー, while フットボール most often refers to American football (アメフト) — the term in this sentence is intentionally ambiguous unless context narrows it.