OP,
Your description of the situation is a little vague and too exclusionary. What do you mean by 'intimately attracted'? And how can traits like 'level of maturity' be ignored? The difference in ages is not an ethical or moral problem in and of itself. But a domineering and mature 21 year old male with a naive 15 year old girl could be problematic. So disregarding 'character traits' makes it difficult, if not impossible, to give a valid assessment of the situation.
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Don't laugh at me, Don't call me names
Don't get your pleasure from my pain
In God's eyes we're all the same
Someday we'll all have perfect wings