[name_f]Heidi[/name_f] seems a little dated next to [name_f]Isla[/name_f] but it still seems usable and if you love it, then you should consider it.
I like:
[name_u]Ruby[/name_u]
[name_f]Cora[/name_f]
[name_u]Julie[/name_u]
[name_u]Alix[/name_u]
[name_f]Daphne[/name_f] (which is way less popular than I thought)
[name_f]Sunday[/name_f]
[name_f]Fiona[/name_f]
[name_f]Phoebe[/name_f]
[name_f]Gemma[/name_f]
[name_f]Libby[/name_f]
and
[name_f]Rose[/name_f]
good luck!
[name_f]Love[/name_f] [name_u]Piper[/name_u] but seems too trendy, [name_f]Isla[/name_f] has a classmate [name_f]Maren[/name_f] (which shouldn’t rule it out all together, but I had also pushed for this before and dh didn’t like it.)
[name_f]Chloe[/name_f] is my guilty favorite, but can’t use it, too popular. [name_f]Maris[/name_f], [name_f]Carys[/name_f] and [name_u]Adair[/name_u] don’t appeal to me. [name_f]Fern[/name_f] is ok but seems to tame…like I picture a very meek/mild person named fern. I like [name_f]Margo[/name_f] but dh said no.
We had [name_u]Ruby[/name_u] high on our girls name before…perhaps it could be added back on. I love [name_f]Cora[/name_f] but it’s my cousin’s kid’s name - BOO! [name_u]Julie[/name_u] is my sister’s name (who died as a baby), I like [name_f]Gemma[/name_f] but too close to [name_f]Emma[/name_f] (who is my other sister who died recently… 
[name_u]Alix[/name_u], [name_f]Daphne[/name_f], [name_f]Sunday[/name_f], [name_f]Phoebe[/name_f] and [name_f]Libby[/name_f] don’t appeal to me, but I do love [name_f]Fiona[/name_f]…maybe I should push harder on that one 
I freaking [name_f]LOVE[/name_f] [name_f]Cleo[/name_f] but dh says it sounds like a TV psychic and refuses to hear anything else about it, lol! I think it’s such a cool name.
[name_f]Isla[/name_f] is very pretty! I think these work well and have the same feel:
[name_f]Stella[/name_f]
[name_f]Scarlett[/name_f]
[name_f]Sylvie[/name_f]
[name_f]Carys[/name_f]
[name_f]Gwendolyn[/name_f]
[name_f]Adeline[/name_f]
[name_f]Olena[/name_f]
[name_f]Olesia[/name_f]
[name_f]Winifred[/name_f]/[name_u]Wynne[/name_u]
[name_f]Thisbe[/name_f]
[name_f]Thera[/name_f]
[name_f]Ondine[/name_f]
[name_f]Theda[/name_f]
[name_f]Theora[/name_f]
[name_f]Thetis[/name_f]
[name_f]Talitha[/name_f]
[name_u]Tierney[/name_u]
[name_f]Nadya[/name_f]
[name_f]Tasmin[/name_f]
[name_f]Nerys[/name_f]
[name_f]Nyree[/name_f]
[name_f]Nia[/name_f]
[name_f]Talitha[/name_f]
[name_f]Ione[/name_f]
[name_f]Illona[/name_f]
[name_f]Iolanthe[/name_f]
[name_f]Ailsa[/name_f]
[name_f]Aislinn[/name_f]
[name_u]Skye[/name_u]
[name_f]Anais[/name_f]
[name_f]Fiona[/name_f]
[name_f]Tess[/name_f]
[name_u]Rowan[/name_u]
[name_f]Moira[/name_f]
[name_u]Darby[/name_u]
[name_u]Kerry[/name_u]
[name_f]Cara[/name_f]
[name_f]Saoirse[/name_f]
[name_f]Enid[/name_f]
[name_f]Delphine[/name_f]
[name_f]Vera[/name_f]
[name_u]Adair[/name_u]
Names to go with [name_f]Isla[/name_f], sorry if I have any repeats:
[name_f]Clea[/name_f]- softer sounding then [name_f]Cleo[/name_f]
[name_f]Freya[/name_f]
[name_f]Olive[/name_f]
Zahli?
[name_f]Callie[/name_f]
[name_f]Luna[/name_f]
[name_f]Eleni[/name_f]
[name_f]Bonnie[/name_f]?
[name_f]Jasmine[/name_f]
Whenever I think of [name_f]Isla[/name_f], I think of [name_f]Freya[/name_f]…and vice versa.
Some suggestions, sorry for any repeats:
[name_f]Maeve[/name_f]
[name_f]Iona[/name_f]
[name_f]Malvina[/name_f]
[name_f]Olivia[/name_f]
[name_f]Violet[/name_f]
[name_f]Davina[/name_f]
[name_f]Elspeth[/name_f]
[name_f]Charlotte[/name_f]
[name_f]Nia[/name_f]
[name_f]Kerensa[/name_f]
[name_f]Ava[/name_f]
[name_f]Nora[/name_f]
[name_f]Fiona[/name_f]
[name_f]Greer[/name_f]
[name_f]Lily[/name_f]
I saw a previous thread that was talking about [name_f]Isla[/name_f] and [name_f]Esme[/name_f] and I must admit I think they are gorgeous together but they might feel too close for you. Suggestions that don’t end in A:
[name_f]Alice[/name_f]
[name_f]Claire[/name_f]
[name_f]Elaine[/name_f]
[name_f]Felicity[/name_f]
[name_f]Giselle[/name_f]
[name_f]Kate[/name_f]
[name_f]Odette[/name_f]
[name_u]Ruby[/name_u]
[name_u]Skye[/name_u]
[name_f]Tess[/name_f]
[name_f]Vera[/name_f]… ok that one ends in A but I like them together
ETA: Perhaps [name_f]Nina[/name_f] instead of [name_f]Nora[/name_f]?
[name_f]Eloise[/name_f] ([name_f]Ele[/name_f]-oh-eese)
I love the name [name_f]Isla[/name_f] and this is another name I like which I think has a similar feel.