There are 2 main things a CIF athlete (ie Sadie) may not do unless they want to put their high school eligibility at risk:
#1) Compete in a Collegiate Track Meet (defined as one in which collegiate athletes are competing for or representing their school).
#2) Compete unattached in an open division competition at a joint sanctioned event
The penalty for a violation of #1 is being declared ineligible for high school participation in that sport for the duration of the student's high school enrollment.
The penalty for a first offense violation of #2 is being immediately ineligible for participation for 2x the number of contests in which the student participated. The penalty for a subsequent offense is being immediately ineligible for 365 days from the second infraction in all sports. The student may petition for reinstatement.
A CIF athlete may compete in unlimited outside track and field competition provided they enter as unattached individuals and abide by all rules applicable to unattached competition (see #1 and #2 above).
The exact definition of a Collegiate Track Meet is still subject to interpretation. Whether one college athlete in one event at one meet can taint an entire meet is not addressed anywhere.
The High School portion of the TEN was issued sanction approval through J Serra. Had the CIF known that a high school student with any remaining eligibility was to be invited to the open division competition section of the event, then sanction approval would not be issued. J Serra may have hurt their chances of obtaining CIF sanction approval in the future.
Sadie could have been fine at the TEN if there was no high school division. Sadie may try to take the argument that her CIF season had not started because she had not yet raced for her high school this season, but that argument will likely not stand.
Sadie is also entered in the 800m at the Azusa Distance Meet of Champions this weekend.