Hi ArsenicYellow,
Thank You for having the courage to post a very sensitive topic/question. I went through a medical trauma during my undergrad and talk about it bluntly/openly in my statement of intent as it has made me a better artist and contributed to my work. You could perhaps take the same approach, simplifying it by saying "I went through/had to work through some very personal issues during undergraduate and believe that ultimately overcoming those personal obstacles has contributed to my work-but unfortunately it also is reflected in my GPA"- something along those lines.
I hope this helps! This said I really think it was a bit inappropriate for a professor to mention that admissions boards don't want anyone with issues/ect. I'm sorry but most artists have issues, hence we make badass art. Art is therapy. You can def over-share to the point where it distracts from your work though/TMI...my advice take the relevant information that explains your GPA, (I went through a very personal trauma) and then tie it back to your art.
Pushing lots of wonderful luck your way!