She hailed "Room to tack!" way too early — can I just ignore it?
No. Under Rule 20.1(a) a boat must not hail before she actually needs to make the tack, so hailing too early does break the rule — but that doesn't free you. Under Rule 20.2(b)/(c) the hailed boat must still respond: tack as soon as possible, or reply "You tack" and give room. After both tack, Rule 19.2(b) then makes the outside boat give the inside boat room at the obstruction. World Sailing Case 33.
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<p><a href="https://sailing.kiwi.nz/upwind/case-33-room-to-tack-too-early/">Source: Sailing Kiwi</a></p>