The name of this movie!?

okay this may be hard for someone to figure out because i only remember so much. i THINK it's a lifetime movie, im almost positive but it might not be. it's where this girl is at a picnic in the park with her family and friends and i remember there was a whole bunch of bikers for some reason.and then later on she gets killed and they find her body in a river.also i think her name was jenny.and the mom solves the murder im pretty sure. i know that there isn't a lot of detail, i remember this movie from my childhood and so only some parts stick out.if you know this movie or even have any ideas please list them! it would help alot.i'd really love to find this movie :)