Why is she angry when i only said the truth?

this friend of mine sat in my lap today and it really hurt, she has a flat hard but and she sat right on my jewels so i told her to get up that her and that her "boney *butt* was stabbing me in bad places" and she got really offended. i kno it could sound kinda mean, but it was all in a jovial spirit and she just got pissed, though i made light of the fact she actually really did hurt me. and i other friends were there and made cracks at me about the whole thing, in the same insulting jovial way. so what is her problem? really she can always dish out stuff but can never take it