Sandy sent her past self to Kamp Koral to destroy the secret formula so it could be safely rediscovered in the future and preserve the timeline, but the episode that introduces Gary reveals that the show takes place a year after the summer shown in Sponge On The Run, so was this a plan in the making for two years? Well, SpongeBob encouraged Sandy to follow her dream to become a scientist when they first met, and maybe Sandy wanted to return the favor by inventing the hydro-dynamic spatula that helped him achieve his dream to become a fry cook since we never actually see SpongeBob find it onscreen in the pilot, which possibly even could've been how Sandy's past and future selves found out they needed to prevent the formula from being created when it wasn't supposed to in the first place.
my interpretation of spongebob "encouraging" sandy to follow her dream of becoming a scientist is... this scene was specifically engineered by the sandys. it's manufactured to facilitate the new timeline.
you can either take this to mean it isn't sincere and their relationship is based on a lie in this timeline (i don't, for the record) OR. you can take this as A) a testament to how much sandy cares about spongebob that she wants to preserve the strength of her friendship with spongebob even under new circumstances and/or B) an attempt to recapture the way spongebob made sandy feel at home and appreciated in bikini bottom in the original timeline, under new circumstances
we are shown in kamp koral that the young sandy is not entirely sincere with her cabinmates, hiding a lot from them - such as the fact she is actively making adjustments to the timeline under the guidance of her older self. since she's only at the camp because of her future self, who she already knows to be a scientist, the young sandy doesn't actually need that encouragement because she already knows she'll be a scientist. but both sandy's knew they needed an organic push to form a strong bond between young spongebob and sandy - so since sandy is said to have felt out of place even at home in texas in the spongebob musical, they play that up for the young spongebob. it's not completely a lie, she did feel like it as an unrealistic goal that would put her at odds with her peers... but its not something that actually bothers her by the time she meets spongebob in this timeline, because of her older self.
as for the formula not meant to be created yet... i think that's a subjective opinion on sandy's part. i think referring to her intervention as "preserving the timeline" is also subjective - it's based entirely on what she thinks is right, based entirely on how she thinks the timeline should go even if it isn't something she ever experienced. it may be based on her findings while studying other dimensions and alternate timelines, time travel has come up enough that she could have studied its effects. but how can you statistically prove that one timeline, one dimension, one universe is the ONE TRUE TIMELINE? logistically, it doesn't make sense.
she wasn't present for friend or foe but she's friends with both plankton AND krabs so reasonably would have found out about their falling out and, while experimenting with multiversal travel discovers variations of the timeline where they don't fall out over the formula as kids (friend or foe: trash bash) or that the formula is a family recipe passed down for generations (dunces and dragons) or that the two simply chose a different pursuit than the krabby patty (bikini bottom 2's cookie bucket) and decided that it seems like the formula being created when the two were children was a chronological anomaly and intervened. but is her perspective a universal truth? i don't think so.
(shrugs) sandy inventing the hydro-dynamic spatula could still tie into this but i don't know.