Meowth and Purrloin I kinda see as playful rivals for Blake's affection, with one being her first Pokemon and the other her second. Mightyena could have been be a White Fang-issue Pokemon, like how every Aqua and Magma Grunt has a Poochyena, only she actually cared about hers enough to raise it and evolve it. Liepard could be Purrloin's mother or father who helps keep the young cats in line, and Umbreon could be a wild one that stole some food and Blake took pity on it.