Well there are reasons why we do not craft selfish spells. This is what the mundane would call 'black magic'. Whilst all magic is colorless, we ascribe a color to magic based on its intent.
Often 'evil' magic is considered black, however if we look at the foundation of the intent, we find that more often than not 'black' magic is founded upon self serving intent, selfishness, greed, the search for power for the sake of power, which power corrupts.
Casting a love spell on another person comes with risks and consequences, I fear that this is but one of them.
I fear that this situation will not end well. I would recommend that the caster releases their victim (oh this is so much a violation of the human will that we can easily call it rape) and do a number of atonement in order to free themselves (slightly) from the coming train of consequences that selfish use of craft brings with it.
If the caster refused to relent, the victim will come to a point where that love/hate aspect will destroy something, or someone - either them self or the object of their conflicted emotions.