As a sibset? They have everything wrong to me, really. Same ending sound, different style / feel, mismatched syllable count. But for some reason I really, really like them together.
I think [name_f]Stella[/name_f] & [name_f]Etta[/name_f] are maybe too similar to be ideal, but [name_f]Stella[/name_f] & [name_f]Hettie[/name_f] / [name_f]Hennie[/name_f] / [name_u]Henri[/name_u] would be cool.
They feel stylistically mismatched, but that’s not a bad thing! I know sisters [name_f]Ella[/name_f] and [name_f]Henrietta[/name_f] (goes by [name_f]Henny[/name_f] usually), so these sound like a match to me.
The styles do feel different but not so far off to be a complete deal breaker and while I don’t usually go for matchy endings, I think it works here since the rest of the names aren’t super similar.
They have a different vibe, but I think they could work - especially with nn [name_f]Hettie[/name_f] and [name_f]Stella[/name_f]!
I wouldn’t pair [name_f]Stella[/name_f] + [name_f]Henrietta[/name_f] together however I think mismatched sibling sets are completely fine and should be embraced. It’s far better to use two names you love then go for a name you don’t love for a more natural ‘fit’
I think they’re fine and actually prefer the long form with [name_f]Stella[/name_f].
I really like these two together! I like [name_f]Hattie[/name_f] as a nn for [name_f]Henrietta[/name_f] - so [name_f]Stella[/name_f] and [name_f]Hattie[/name_f]?
I think [name_f]Stella[/name_f] and [name_f]Henrietta[/name_f] are beautiful together. I actually gong think they are mismatched at all as they carry that old school classic vibe. I do sort of want to make [name_f]Stella[/name_f] into [name_f]Estelle[/name_f] but I think [name_f]Stella[/name_f] is perfect too
Thanks all! 
I agree that names don’t have to be super matchy, but I often like sets that share the same vibe. This just slightly off thing in a pairing would usually put me off, but I really like it here. Thankyou for your comments!
Ignoring my opinions on both of the names individually, [name_f]Stella[/name_f] and [name_f]Henriette[/name_f] sound fine.