I feel that the rest of the song lyrics provide the required context to interpret the line in question. I don't claim any singularly "correct" interpretation of course, just my personal take.
I've chosen a few opening lines, (which usually set the general tone / direction for the rest), as a kind of "explanatory preamble" to the line in question. They are:-
(please note that I am paraphrasing as a direct translation often makes no sense in English)
The first 2 lines depict the author's disappointment / unhappiness / dissatisfaction with "Life", "the Human Condition", "this cynical Mundane world which showcases the worst of human nature and motives", as she sees it.
And in leaving all these "Worldly Injustices" behind, seek out her own lonely path to personal fulfillment and inner happiness -- 紛紛擾擾這人間缺個公道 ...我辭三界 別五行自顧去逍遙.
But, there is a price to be paid for her "conscientious endeavors", and the "price" is:-
此去必經年, 荒野寒暑換紅顏, (Note:- And here is where the Commentators diverge in their interpretations)
There appear to be 2 interpretations, (as I see it):-
Willingly change her "紅顏", (youthful good looks), to resemble / be similar or bear a likeness to the 荒野寒暑, (not necessarily to be "ugly", but take on the "toughness", "resilience", "survivability" to be in natural conformity with the wild environment, a "Me Tarzan, you Jane" situation)
Give up, discard, "sacrifice" her "紅顏", (over the years, 此去必經年), "in exchange" for the "opportunity" to live in a 荒野寒暑 environment which do not have the 而置身事外的君子在一旁冷笑, 紛紛擾擾這人間缺個公道 which she despised, and 十寸光陰換一錢 is a worthwhile exchange.
Which would I chose?
#2, I suppose.