Funny enough Bubbeline is an actual tumblr romance with all of the bad behavior and self-destruction entailed.>Marceline
Doesn't Respect Authority
Emo version of a Maniac Pixie Dream Girl
All of the above leads to a persecution/insecurity complex that she projects onto others and causes her to flip out if she feels manipulated.>Bubblegum
With the new episodes we see she's just as if not more controlling as Hunsoon (Marcy's Dad) and her bullshit led to the Gumbald-Bubblegum skiff) and she was a terrible "mom" during the entire Lemongrab arc (especially making Lemonhope a sleeper cell child soldier to keep control).
She's a major authority in the land and she still acts like a Machiavellian dictator on a massive ego trip. Even muh "Varmints" didn't fix this in the long run, it only taught her how to hide and lie about her bad behavior better.
Used to be Maniac Pixie Dream Girl about muh science but now is just a complete cunt focused on control and power.
Bubblegum's actions have lead to most if not all of her problems but she wants to have a similar victim complex like Marcy. However she will always belittle and manipulate Marcy because "The pain of being a princess" will always be bigger than Marcy.
So they made them lesbians for pandering when they're the most incompatible people in the series. This isn't even an "opposites attract" thing, they are horrible for each other and the relationship would be considered toxic and abusive by Tumblr if they weren't scissor sisters.