1. It seems like it would be difficult to misunderstand "Was 1NT forcing?" Not that it matters to the ruling.
2. The question was asked and answered after dummy came down. We are now in the play period. This matters (see below).
3. Jillybean told the Director that had she known that 1NT was forcing, she would have bid 3
♥ over 2
♠. The advisability of doing so is not relevant to the ruling, only the possible outcome(s) are relevant.
4. Failure to announce 1NT forcing is an infraction of the Alert Regulation and hence of Law 40B. (See the definitions above).
5. Such infraction is considered MI "absent evidence to the contrary" (Law 21B)
6. It is too late for Jillybean to change her last pass, since we're now in the play period (see #2 above).
7. If the TD judges that the offending side (OS) gained an advantage from the irregularity, he awards an adjusted score. (Law 21B3).
It seems to me that the OS *did* gain an advantage from their infraction/irregularity, because if Jillybean had been able to bid 3
♥ over 2
♠, the OS would have had to decide whether to allow that contract to stand, double it, or bid 3
♠. Since they didn't need to make that decision, they gained an advantage.
The TD, called at the time dummy went down, should find out what the OS might have done over 3
♥ and instruct the table to play out the hand, and to notify him of the table result. Now he may adjust the score to whatever would have happened in 3
♥, or in 3
♥ doubled, or in 3
♠ (there may be other possibilities). He may award a weighted score.
What if there was no damage, if none of the possible results would have given the non-OS a better score than they got at the table? In that case it seems to me there should be no adjustment, even though Law 21B3 doesn't refer to "damage" but only to "advantage". There is another consideration though: if this was Matchpoints (the OP doesn't say) then it's possible there was (or wasn't) damage to the Matchpoint (MP) score. If there was damage to the MP score, adjust. If there was no damage because the Non-OS would have obtained the same MP score they got at the table, one might adjust as a message to the OS to remember to announce 1NT Forcing. Some will see that as silly. I suppose TD could just tell them.
The details of any score adjustment depend on the four hands, and we don't have those.
I would not give the OS a procedural penalty unless they've made a habit of this infraction and have been warned about it before.