If I could talk to the writers of the show, I'd say, "Hey, remember that griffon from the fourth episode of season one? No? Well, everyone else seems to remember! So, could you give us a little summer love and PLEASE HAVE A GILDA REDEMPTION EPISODE!?!?!?!"
The Griffon is the natrual enemy of the horse ( Unless under certain circumstances, which might or might not hold true for Gilda ). Also an obligate Carnivore. Food served in Ponyville would slowly kill her, which means that it can only stay there for a short time, unless she feasts on those ponies. Indeed it is likely that Gilda would not even have entered Ponyville if she and Dash were left alone. Unfortunately, they were not left alone, their quality time disturbed by the most annoying creature in all of Equestria, the one every non-Pony seems to take a naturally dislike to, Pinkie Pie! Hence they enter Ponyville, with Gilda pranking some Ponies in order to brighten up her mood. And if you are a Griffon, this means scaring them. That yellow Pony with the pink mane? Was at the wrong place at the wrong time, not a specific target. Then came the party. Cleverly set up by the one that does not want her and Rainbow Dash to be together. The one who probably wants to split them! She knows that she has to stay calm. If she slips, she might break some Ponies, someone could die. Then it hits her, pank after prank. Obviously the work of Pinkie Pie! No? It was Rainbow Dash? A manipulation by the Pie. Even worse, Dash wants to stay with Pinkie instead of her? Her heart is broken, sadness fills her mind. She is unsure what to do, let's out an half-hearted insult and leaves.
You must have misunderstood the purpose of Gilda. She iconifies a bad person to be friends with: she is shallow, belligerent, self-centered, and a thief. She's not supposed to be endearing. You're not supposed to like her, because she is the one who was making all the wrong decisions. I'm guessing you either know someone IRL like Gilda that you somehow like, or you are just the kind of person she is.
It would actually be really easy to understand Gilda's actions, if we were given any. We're left to assume she's just another punk. This fandom sure does like to demonize the good characters and frantically find reasons to excuse the bad actions of the evil characters.
Because "For the Evulz" is a weak motive. And with the mythological background of the Griffon, Gilda makes a lot sense. Even without it when one sees her as a girlfriend of sorts to Dash. Or just another character pissed off by Pinkie. That Episode could aswell be called "Pissing the Griffon off"...
Meanwhile, it is easy to see that Pinkie is not nice. Chances are that she is some bigot, or otherwise just a jerk. Aside from not leaving Gilda alone, she: - accused a reformed Criminal of Canibalism, sabotaging any afforts to clear the situation. ( Also counts as Bullying a Dragon, since said former criminal is also basically a Pony God ) - spread and likely also created rumors about someone being an Evil Enchantress ( could aswell have lead to burning zebra....) - manipulated her rivals in a contest to eat each others entries - willingly made a conflict between a native and an invasive Species worse - clearly mistreats her pet - kidnaps Spike for the sake of it - once created a clone army which wreaked havoc And now the silly reason: made Fluttershy cry...twice!