Choose for me !

[Lillylola]

Helena
Christina
Isabella

Helena: love it! It's such a beautiful classic name. I don't normally like longer names but I do prefer Helena to Helen. As pp have said though there are different pronunciations for it.

Christina: it's a nice name. Not very common nowadays. I don't like it as much as Helena though.

Isabella: I'm not keen on this name, for me it seems to frilly. I do love Isabel though

My name is Helena and I was always the only one in my school (went to several due to my dads job needing us to relocate quite a lot) . I have always liked my name.

We had Christiana on our list. I love iana sounding names. We also had Dahliana .

Helena. It's beautiful and I'm not sure I've ever come across one in real life!

Isabella second- it's lovely but ridiculously popular- and I really don't like Izzy at all (which people would call her inevitably).

Don't like Christina at all.

Dd was nearly a Helena. It’s a lovely name, but I’m quite glad we didn’t choose it in the end, as there are a lot of Eleanors around and I think it could have been misheard as that too often. I think I prefer Helen now.

Christina is due a comeback.

Not another Isabella.

Christina

Love Isabella, also Isabel or Isobel.

Dislike Christina and Helena, seem middle aged women names to me

Like Helena. Love Christina (knew an incredibly chic Christina who was a very lovely woman). Cannot stand Isabella. In the 00s, I taught approximately 3699863 of them and the various diminutives.

Christina/ Christiana! Beautiful names.
I like Helena too but would it be ‘Hel-AY-na’ or ‘Helen-a’?
Isabella is so overdone

Helena can also be Hel-ee-na

Christina Helen. Perfect.

All nice names & I probably slightly prefer Christina
I know at least 3 different pronunciations for Helena.

HuhLEENuh is one I find most natural.
Hey-LEY-nuh
Heh-LEY-nuh
Heh-LEEN-uh

We had a female friend called Christian. That’s nice. Also christiana is nice too.

Helena - really lovely, wonderful history, not overused - easier if you want the Helen-a pronunciation mind you. (only minor thing is if she nn herself will likely be Nell or Ella and there are a lot of those - but there is Lena too).

Christina - it is nice though not as lovely as the other two IMO... but for me the big problem is Chris is such a dull nn - you could try imposing Christa, or Christy, but you can’t stop it.

Isabella - lovely, but there are so flipping many Isabella/Isabel/Isobel/Isabelles ... I think it needs to retire now.

Ysella (Ee-sella) is a Cornish alternative, or Ishbel a Scottish one. Or Annabella or
Arabella.

Helena

Isabella - it's just got a lovely sound to it. The other two sound slightly dated to me - sorry! But do love Isabella.

Helena - classic, lovely, mellifluous sound. This would be my first choice.

Christina - dated, will get NN Chris/ Chrissy.

Isabella - nice but there are millions of them and also millions of Izzys and Bellas.

Helena would be my first choice - elegant and Shakespearean. It also has a lovely sounding nn in Nell and because it has never been very popular in the UK, it feels quite timeless imo. I prefer the Helen -ah pronunciation and thanks to Bonham Carter, I think in E&W most of the time you'll get that.

Christina would be my second choice - it feels a touch dated (70's/80's) but is a lovely name and the nn Kit/Kitty is very cool. Isabella is pretty but is quite popular and I personally prefer the simpler Isabel.

All 3 are good names. If one is closer to your heart just use it without hesitation.
My take:
Helena - beautiful classic name, stylish. More soft and gentle in sounds than the others. The different pronunciations would put me off a little. Love Nell as a nickname.
Christina - this and Helena are my favourites. Traditional, stronger feeling than Helena, not often used, lovely nickname Christy. Feels feisty, which is good. I like Christiana too, but the extra syllable means it is more likely to be shortened, which may matter if you prefer the full name being used.
Isabella - nice enough, again strongly traditional, but frillier than the others which doesn't appeal to me. Over-used. I prefer Isabel, which seems somehow smarter and neater.

I'm torn between Helena and Christina as first choice. If you're pronouncing it Hell-uhn-uh with emphasis on the first syllable, then I'd probably choose that.

Just to add, I love Kit/Kitty nickname for Christina. If she was getting this nickname I would put Christina as first choice.

Christina is nice - too many Isabella's and I don't know how to pronounce Helena

Helena is lovely. A few other thoughts (sorry!)
Estella (same 'clean lines' as Helena)
Christabel, Georgina/Georgiana, Henrietta (nn Ria), Francesca (nn Cesca), Emmeline, Felicity
Lydia, Sylvia, Julianna, Rowena, Susanna

Christina, lovely name. Not keen on Christiana.

Helena has too much potential for mispronunciation and Isabella is far too popular.

Christina & don’t shorten it , Christina is beautiful.

I was a bit "meh" about all your names until I saw Christiana, love it. Amongst your chosen names I'd pick this one hands down.