Unfortunately this happens, but thankfully rarely. It reminds me of another member who thanked me publicly for my answer, then wrote me a long and hateful message calling me rude, and telling me to never help him again. It wasn't the first time I'd seen a petty and selfish retort on italki, so I added that member to my mental "don't help, don't communicate" list, and moved on.
Your answer to her question was perfectly appropriate (as was Su.Ki.'s), but it's clear she expected a different answer, in spite of not indicating that at all. I'm a little surprised that a learner who's still trying to come to grips with another language can get such fixed ideas in her head. Still, that's not our problem! :)