That is a very slight possibility, but it is possible. 11 yr olds DO commit suicide.
I do wonder though if they do so without ANY previous warnings or attempts or threats. We have not heard that she was depressed or really sad in the previous weeks.
And she was very very close to her 13 yr old sister. My gut tells me she would have left her a note, an explanation, if she was going to jump off a bridge.
I don't get that feeling from her. She had good grades in school, many friends, played sports, and her recent pictures, like the one in the hat, showed to me, that she realized she was actually quite pretty. She was in the gawky awkward phase that most 11 yr olds go through, but I think she saw that she was going to be a swan. I think she was looking forward to her future, I don't think she was hopeless or depressed. imoo