(A coordinating conjunction is a word that joins two elements of equal grammatical rank and syntactic importance.) (website definition)
Grace is saving money so (she can buy her own horse.)- dependent (so acting as so that/in order to).
But what about the other conjunctions.
Grace is short of money but she can still buy her own horse.
Grace is short of money yet she can still buy her own horse.
Grace is short of money and ,for now, can still buy her own horse.
So they are not joining elements of 'equal' grammatical rank.
Is this usage correct; joining dependent clauses this way.