A good piece of writing so far.  I'm a bit confused over some of the reasons you wrote about why she did this to him.  How could his confidence in talking to women make the other office workers disrespectful of Mandy?  If she was so unhappy with him, why didn't she tell him?  I assume that he got evaluated every so often, or just fire him?  I'm looking for a more solid reason why she would go this far.  A more solid reason could be that's she's attracted to him and he rebuffed her advances, but was flirting with other female co-workers.  I'm just not a fan of the old "I shrunk him, because I felt like it."  But otherwise the story has grabbed my attention and I'm interested to see what her plans are for him.