Anim Pakal was creating tokens even though she had a -1/-1 counter on her from attacking Tasha after activating her first ability:
"Until your next turn, whenever a creature attacks you or Tasha, put a -1/-1 counter on that creature."
Since it was my opponent's turn, her ability would be placed on the stack first, and THEN mine would go on top. So technically Anim would never have had a +1/+1 counter placed on her because as a state based action they would both be removed and then it would recheck the triggered ability.
See Rule 122.3:
If a permanent has both a +1/+1 counter and a -1/-1 counter on it, N +1/+1 and N -1/-1 counters
are removed from it as a state-based action, where N is the smaller of the number of +1/+1 and -1/-1
counters on it. See rule 704.
and Rule 704.3 (edited to the specific section of the rule):
If any state-based actions are performed as a result of a check, the
check is repeated; otherwise all triggered abilities that are waiting to be put on the stack are put on
the stack, then the check is repeated. Once no more state-based actions have been performed as the
result of a check and no triggered abilities are waiting to be put on the stack, the appropriate player
gets priority.
and rule 704.5q:
If a permanent has both a +1/+1 counter and a -1/-1 counter on it, N +1/+1 and N -1/-1
counters are removed from it, where N is the smaller of the number of +1/+1 and -1/-1 counters
on it.
She should not have created any tokens, because the triggering event would be rechecked after removing both types of counters.