I voted for Lenna, because it's different but familar, and easy to spell. However, I also really like Lillian, Carolyn, and Isla a lot!
Not a fan of Mikayla, Katelyn, or Cameryn (it means crooked nose!), and Hallie is sweet but sounds like a nickname to me (though Lenna could be a cute nn for Lillian or Carolyn...)
1) Lenna Jae
2) Lillian Jae
3) Carolyn Jae
4) Isla Jae
I voted Isla, I like Lillian, but there are a lot of other Lily- names out there (most of which I dislike, esp. Liliana, I despise the ah-na sound so so much!) and I think Isla is a lot more stand alone so its as popular as it seems as opposed to be one of many variations if that makes sense.
Hallie seems too nicknamey for my taste, completely reminds me of the Parent Trap, and could be mispronounced as Hailey. I really like Halcyon, but that ight be too out there.
Lenna - If you're pronouncing it like you would pronounce Lena then I love it but I would use the Lena spelling, if you're pronouncing it Len-na then I don't really like it, mainly cause it's a bit too much like Jenna which is very dated to me.
Mikayla - I really like the Michaela spelling, but all of the other spellings I don't find appealing at all.
Katelyn - I'm not a huge fan of -lyn names, I prefer the Caitlin spelling, I really like the nn Katie.
Cameryn - NMS.
Lillian is by far my favorite! I adore it. I also like Isla. How do you say Lenna? I like Lena, but I feel like Lenna should be LEN-ah, which I don't quite like as much. Lillian gets my first vote, followed by Isla. I think Lillian Jae or Isla Jae are both lovely. Is there significance behind the mn Jae? I don't find it very feminine, and it just sounds like an initial to me, but I could appreciate it if it has significance. :)
I love the name Mikayla, but how about if you spell it Michaela? Michaela Jae , I love how the ae looks together! I also like Isla, but I think the name is going to be really popular really soon. Hallie is pretty, but doesn't feel complete, Katelyn is nice, but I prefer Kaitlyn spelling and I'm not a fan of any of the other names. Jae is really pretty.
I love Lillian, Michaela (not Mikayla, though) and Isla.
I love Lena pronounced Lenna—that's one of the pronunciations I've heard most, actually.