Headcanon: sisters. I would imagine Blossomforth being the awkward one and Helia being the smart, elegant one.  
Reminds me of two people.

Why change it.

SO TRUE.

Maybe Blossomforth was supposed to be in a scene that was cut?

@Turnways_Flip  
Okay, so the animators messed up with Helia instead of Blossomforth or the credits people put Blossomforth instead of Helia, and someone should have thought that through. At this point, Blossomforth may have the established identity, but I’ve seen Helia more often paired with Thunderlane so this didn’t faze me too much.

@DuskFox  
*in other colors

That was Blossomforth, she just accidently got dyed with other colors.

This is the WORST. POSSIBLE. THING. EVER!

The fail lies in the animation error:
 
Pony listed in credits as Blossomforth, Blossomforth did not appear.

@anonymouspegasus  
The credits for this episode said that Blossomforth was voiced by Spitfire’s VA. That’s the implication in question. And it really is disappointing even if you don’t like Blossomforth (and who the hell doesn’t like Blossomforth), since Blossomforth is a well-established identity attributable to a pony with a specific appearance as seen both in the dialogue of Hurricane Fluttershy and in the merchandising. In other words, it’s a fail. This could be on Failblog, that’s how faily a fail it is.

We all feel like that, OP. :)
 
But honestly? They have no way of knowing that we love Blossomforth. And Helia’s been around before her.
 
Don’t even get Wild Flower into the discussion because it just complicates things more. See, you could take Blossomforth and Helia as separate characters even if the freckles are pretty obvious, but Wild Flower and Helia even share a friggin’ cutie mark. Since Wild Flower’s a Wild Fire swap too, no wonder people don’t take Helia seriously as a character either…

Hold on.
 
In “Hurricane Fluttershy”, Blossomforth merely passed by Rainbow Dash from what I remember. Helia, this turquoise pony, was almost constantly with Thunderlane.
 
That doesn’t sound like “replaced” or “implied” anything.

@Psychopomf
 
That sounds like Caramel’s gig.

I just like the idea that Thunderlane is a lovably scamp who tries to go on dates with a different mare every so often, but keeps screwing up eventually and getting dumped.
 
Leaving him to sob to his supportive mare friends that totally aren’t his mare friends if you know what I mean.

@P3FOYFN  
Wonders, or blunders?

Dangit I want my fruit roll-ups pony now!

Implied, or implode?
 
 
@Princess♠Molestia  
She changes her hair colour every week-and-a-half.
 
@CallMeAl  
Duke’s colourblind, kid.

@Princess♠Molestia  
See OP? This kid’s got the right idea.

I just headcanon that Wildfire really likes hair dyes and changes her style like once a month.
 
Makes it more fun