“quickly lift up her hands to God with tribute.” The Hebrew is more literally, “Ethiopia will cause her hands to run,” that is, run to give tribute to God, which comes from the culture and the context. Someone giving tribute to a ruler would usually kneel or bow low before them and stretch out their hands to present the tribute or gift. “Ethiopia” here is presented in the figure of speech personification. This is not a metonymy, with “Ethiopia” being put for the people of Ethiopia because the pronoun is singular.
[For more on the figure personification, see commentary on Prov. 1:20, “Wisdom.”]