Yes, I do think that Ella Long is a lot of L back to back. Even Ellie Long is easier to say. Since you asked earlier:
Names with "El" in them...
Ariel (prn AIR-ee-el or AHR-ee-el)
Annabel or Annabelle (I prefer these spellings over Anabelle)
Mariel or Marielle
Mirabel or Mirabelle
Delaney (little bit of a stretch, but I think Elle could work. Laney is cute, too)
Stella or Estelle
Gabrielle or Gabriella
I'm sure there are tons more, haha, but my brain is spent!
All those suggestions said, I'd probably choose Charlotte Kathryn over Ella (or a name that you'd give so you could regularly use Ella) since the last name is Long. Sorry! (If you liked the full version or an alternative nicknames for one of the above, I think they'd be great though... Annabelle Long nn Annie is super cute!) I think these would be pretty, too:
Anneliese Kathryn Long (nn Annie/Anna, Lissy, Liese)
Emmaline Kathryn Long (nn Emma or Lina)
Scarlett Kathryn Long (nn Arly, Carly, Lettie)
Ivy Kathryn Long
Violet Kathryn Long
Eliza Kathryn Long
Lydia Kathryn Long (love this alliteration)
Tessa Kathryn Long
Names with 'Bella' in them generally become shortened to Bella, not Ella although Arabella and Annabelle are very pretty.
Some names that could be shortened to Ella-
Dylan, Hudson, Amelia Kathryn Long
Dylan, Hudson, Mirabella (nn. Ella) Kathryn Long
Dylan, Hudson, Victoria (nn. Vita) Kathryn Long
Charlotte is sweet, rather popular. It fits better with Dylan than Hudson as Dylan's trendier.
Ella seems incomplete. Some long forms (no pun intended): Annabella, Arabella, Eleanor, Isabella, Mirabella.