Who owes who money?

Python 3, 173 bytes

a=lambda:input().split()
m={x:int(y)for x,y in zip(a(),a())}
l=lambda k:m[k]
while any(map(l,m)):d=min(m,key=l);s=max(m,key=l);t=min(m[s],-m[d]);m[d]+=t;m[s]-=t;print(d,s,t)

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-6 bytes thanks to ppperry using dictcomps instead of dict of a listcomp