If you want to see her breasts, your only choice is Pickup on 101.
That link leads to the entire film. The shower scene begins at 11:07.
Some years ago, Brainscan did some pretty decent collages from this film (actually, they are brilliant collages, given the poor quality of the VHS which is the only known source of this film):
One last note, unrelated to nudity: There is no need for a DNA test to determine Charlie Sheen’s paternity. A young Martin Sheen in this film looks and sounds almost exactly like Charlie.