From a writing viewpoint, the temptation is to get my characters to use magic to get them out of each and every trouble. One great thing about the conflict between Eileen and Jenny is the former can't do this. If anything is guaranteed to hack Jenny off in a very big way, it would be Eileen doing this. Also Eileen is well aware she can't "magick" the problem of the Fairy Queen sticking her oar in either.
Brankaresh gave in to the biggest magical temptation of all - to use it to gain power and not to be overly fussy as to what to do to improve his magical skills. I think it would have been unrealistic not to have at least one character be greedy, power seeking etc. You get such creatures in all worlds - and a right pain they are too but Brankaresh's attitudes, actions and motives push The Trouble With Mother forward.