に話す

talk to someone

→ に
phrase Very common #689
talk to someone に marks the person you speak to. This is a neutral expression.
JA: トムがメアリーに話すよ。
EN: Tom will talk to Mary.

バーニーに話すって

You said you’d talk to Barney?

— ドライヴ (2011)

「今からブルネルに話すところよ」とスパーホークは言った。

“I’m just about to talk to Brunel,” Sparhawk said.

トムがメアリーに話すよ。

Tom will talk to Mary.

お前が蝶衣に話す約束だろ?

You promised you'd talk to Dieyi, didn't you?

— さらば、わが愛/覇王別姫 (1993)