Congratulations 
Firstly [name_f]Ella[/name_f] is gorgeous!
[name_f]My[/name_f] thoughts on your list…
[name_f]Lila[/name_f] ~ I think this name is beautiful bright, spunky, feminine with an upbeat jazzy vibe. I think [name_f]Lila[/name_f] could be a bit matchy repeated L & A sounds both four letters but just about doable. I think [name_f]Lola[/name_f] would work better due to the strong ‘o’ sound. Other ideas could be [name_f]Lyra[/name_f], [name_f]Lilac[/name_f] & [name_f]Delilah[/name_f].
[name_f]Ariana[/name_f] ~ is feminine, elegant, bright and has a strong princess sound. I think [name_f]Ella[/name_f] & [name_f]Ariana[/name_f] work however not a favourite pairing [name_u]Aria[/name_u] I think is a better fit.
[name_f]Olivia[/name_f] ~ isn’t my style personally I’ve never been a fan of [name_f]Olivia[/name_f] I don’t like how the sounds roll together the o with the l into via isn’t attractive to me. However does work with [name_f]Ella[/name_f]. I prefer [name_f]Olive[/name_f]. I actually love [name_f]Olive[/name_f]! [name_f]Ella[/name_f] & [name_f]Olive[/name_f] would be sweet. I also like [name_f]Livia[/name_f], [name_f]Livvy[/name_f] & [name_f]Liv[/name_f] they all sound wonderful with [name_f]Ella[/name_f].
[name_u]Eden[/name_u] ~ a lovely biblical place name that feels modern yet classic all at the same time. [name_u]Eden[/name_u] does work with [name_f]Ella[/name_f] however I think using another ‘e’ name could pigeonhole you into using e names for future children so I wouldn’t use. Other ideas could be [name_f]Clover[/name_f], [name_u]Wren[/name_u] & [name_u]Arden[/name_u].
[name_f]Amelia[/name_f] ~ granted she is popular but a lot of the names on your list are popular so I wouldn’t rule her out. [name_f]Amelia[/name_f] is lovely a strong classic very elegant and I love the historical references to [name_f]Amelia[/name_f] [name_f]Earhart[/name_f]. [name_f]Ella[/name_f] & [name_f]Amelia[/name_f] work well. You could use [name_f]Amelie[/name_f] or [name_f]Amalia[/name_f] for a less popular option.
[name_f]Margot[/name_f] ~ classic, elegant, timeless and sounds beautiful with [name_f]Ella[/name_f]. [name_f]Gorgeous[/name_f] sibling set. Personally I think both sibling sharing names meaning [name_f]Pearl[/name_f] isn’t a big issue and actually a sweet way to tie them together! I love [name_f]Ella[/name_f] & [name_f]Margot[/name_f] together. Other ideas could be [name_f]Beatrix[/name_f] & [name_f]Phoebe[/name_f].
[name_f]Orli[/name_f] ~ feels a bit random with [name_f]Ella[/name_f] I think [name_f]Orla[/name_f] would be a better fit.
[name_u]Willow[/name_u] ~ a name that has suddenly increased popularity so feels very current whilst having earthy whimsical undertones. [name_f]Ella[/name_f] & [name_u]Willow[/name_u] sound great together. [name_f]Willa[/name_f], [name_u]Juno[/name_u] & [name_u]Juniper[/name_u] could also work.
[name_f]Freya[/name_f] ~ another name that has increased in popularity and is now a firm favourite amongst us Brits! [name_f]Ella[/name_f] & [name_f]Freya[/name_f] definitely work. [name_f]Faye[/name_f], [name_f]Athena[/name_f] & [name_f]Hebe[/name_f] could be other ideas.
[name_f]Sadie[/name_f] ~ a lovely vintage name really spunky and upbeat. [name_f]Sadie[/name_f] & [name_f]Ella[/name_f] do work but not one that I would automatically pair together. Some other vintage ideas could be [name_f]Hattie[/name_f], [name_u]Ruby[/name_u] & [name_f]Tansy[/name_f].
[name_f]My[/name_f] favourite from your options is [name_f]Margot[/name_f]. I think [name_f]Ella[/name_f] & [name_f]Margot[/name_f] is beautiful. [name_f]Margot[/name_f] [name_f]Rose[/name_f] is stunning.
[name_f]Hope[/name_f] this helps