Bubble and Flower have been against each other since episode one of BFDI. Flower's rude behavior has forced Bubble to stand up to her on a couple of occasions. Even though they are on the same team in BFB, they don't seem to as hateful towards each other like before.
Episodes suggesting a conflict
In "Take the Plunge: Part 2", Bubble defends Teardrop when Flower calls her stupid. Flower demands that Snowball beat Bubble up, but he refuses. However, Blocky agrees that he will beat up Bubble, much to Flower's delight.
In "Sweet Tooth", Flower steps on Bubble's lent cake out of anger before judging it, then gives it a low score for looking terrible.
In "Hurtful!", Flower pushes Bubble into the metal furnace. During the challenge, when Flower demands that Bubble help her over the rock wall, Bubble denies her request, saying that Flower will have to do it herself. Flower tells Bubble that Bubble isn't nice. Bubble continues to refuse to help Flower over the wall, so Flower threatens to and then actually pops Bubble. Once Bubble catches back up with Flower, she helps her over the wall, but she's "only doing this because" Flower will kill her if she doesn't. Bubble tosses Flower up to a spot with a boxing glove trap, likely a coincidence. At the final leg of the contest, Leafy accuses Bubble of preferring a friendship with Flower, which Flower claims is true. Bubble denies this, but Flower notes that Bubble helped Flower over the rock wall, which shocks Leafy. Bubble tries to explain that it was only because Flower threatened her, but Leafy cuts her off, stating that their friendship is over, to which Flower exclaims her friendship with Bubble has just begun. With a smile, Flower demands that Bubble throw her out of the volcano, but Bubble turns around and drops Flower into the lava.
In "Insectophobe's Nightmare 2", Flower demands that Bubble apologize for not handing over her immunity, but not before pulling a "you know exactly the reason" thing. Bubble angrily refuses to apologize for this. Leafy apologizes in her place, which Flower accepts.
In "Return of the Hang Glider", Bubble seems perturbed by the sight of Flower biting a chunk out of Announcer. Flower has held a grudge because Firey, Leafy, and Bubble had all killed her, so she doesn't want any of them to win. When Flower is recovered and asks everyone why they aren't celebrating, Bubble confronts her, saying "Flower, I'm tired of this... I mean I'm tired of your self-centeredness. I'm tired of the way you act around us. You know what that means? I'm tired of you!". She tells Flower that her unpopularity is her own fault. Obviously, Flower doesn't take well to this and goes on a rampage destroying recovery centers, starting with the BRC. Once she's destroyed all the recovery centers, Flower killed Bubble, which for the moment seemed permanent.
In "Return of the Rocket Ship", when Flower accidentally falls on Team Ice Cube!, she says it's no big deal since this isn't even the first time she's killed Bubble and brings up the finale as an example.
In "Getting Teardrop to Talk", when Flower says "Observe me please!", Bubble only says "I'm a bember!".
In "Get to the Top in 500 Steps", when Flower volunteers to run for her team, Bubble just says okay.
In "What Do You Think of Roleplay?", seeing Snowball pop Bubble made it clear to Flower and Ruby that neither of them were the impostor on their team.
In "Return of the Rocket Ship", Flower points out how the alliance is only Bubble and Ruby. When Ice Cube decides to join iance, Flower says she can't just do that but Bubble hushes Flower and tells her to let Ice Cube believe what she wants.
In "Take the Tower", Bubble tries to impersonate Flower in order to infiltrate the other team's tower.
Episodes suggesting a friendship
In "Getting Teardrop to Talk", Bubble tried to talk Lightning out of zapping Flower.
In "What Do You Think of Roleplay?", Bubble forgives Flower for her past actions to prevent her from being eliminated.