Giggles is a character I like. She is kind, caring, and sweet. But she can use a bit more development. She is mostly just a female placeholder like Toothy. She tends to adapt to a situation for an episode. That being said, she does have a personality to her somewhat.
Let's get the elephant out of the room: Her cheating problem. She does seem to be a cheater. She dates and dates, and dates. That is arguably her personality. This is supported but the fact that her smoochie is valentines themed. She may even intentionally cheats in the episodes themselves as she occasionally jumps to another boyfriend after dating one in episodes such as Wipe Out! or Cold Hearted. She also does flirty gestures a lot too. She even goes up to random people and flirts when them. I'm pretty sure her boyfriend is Cuddles.
Next thing is her brave and heroic personality. In some episodes, she'll act as a brave hero. This is seen in Every Litter Bit Hurts and Dunce Upon a Time. She is not reckless or mischevous like Cuddles either, and acts more wiser than him. There's even specific moments of her noticing hazards and ways to get injuries.
She can also be screamish, and can easily be traumatized. She nearly pukes when Cuddles' head busts open and his blood is splattered on Lumpy's eyes, screams regulary when blood is splattered on her and have notice Lumpy's privates and screams very loudly. She also cries at other's deaths such as in Happy Trails Pt. 2: Jumping the Shark, Boo Do You Think You Are?, and See You Later, Elevator.
So overall, she does feel like a placeholder at times and often appears to date other characters or do her titular scream but she does have a personality to her. I rate this character a 7/10.