The best she can hope for is 2nd place.
Let's assume that in each event, there is a 103-way tie for first place. Jessica finishes 104th with a score fractionally below the leaders, and the remaining 7 competitors score precisely zero points.
Let's also assume that the winning scores in each event are equal to $X_i$ for $(1 \le i \le 7)$. So competitors who finish among the joint winners in all seven events will achieve a total score of $T = \sum^7_{i=1} X_i$, and Jessica's total score will be $(T - \epsilon)$ points, where $\epsilon$ is some small value.
If $m$ is the event where the joint winners achieved the highest score (i.e., $X_m > X_i \ \ \forall i \not= m)$, then Jessica will achieve the best position if as many as possible of the winners in event $m$ score zero in at least one other event. Since there are seventeen possible places that they can take in the remaining six events, that means Jessica can beat at most 102 of them.
So her best possible finishing position is $104 - 102 = 2$.
(Thanks to Duncan for pointing out the glaring error in my first effort!)