I’m stuck between the two, I really love both of them but they have such a different feel and I’m not sure which one im leaning too sou figured I’d see how others feel about the names
I have to say that I prefer [name]Thea[/name] to [name]Cosima[/name] but both are lovely.
Have you considered how they sound with your last name? That may help you decide.
I prefer [name]Thea[/name] spelled this way as oppose to [name]Theia[/name].
I like [name]Thea[/name] (spelt this way) more than [name]Cosima[/name] but agree with bonnielyn in that I would probably decide by hearing which sounds best with your surname.
I would have picked [name]Cosima[/name] but I like the traditional Greek spelling on [name]Theia[/name] so I am picking that. [name]Theia[/name] is a gorgeous name!
[name]Thea[/name] is near and dear to my heart. I also love some of the longer names for it: [name]Althea[/name], [name]Anthea[/name], [name]Theodora[/name], Philothea.
But honestly, [name]Cosima[/name]'s great too. They’d make good sister names, I reckon.
I love Greek names, but these seem plain to me. [name]Cosima[/name] is slightly more interesting, but I’m not a fan of ‘th’ names generally.
I really like [name]Cosima[/name] for you.
[name]Theia[/name] is ok, but I adore [name]Cosima[/name].
I’m not fond of [name]Theia[/name]/[name]Thea[/name], personally, but I adore [name]Cosima[/name]. I think it’s lovely.
I’m definitely on team [name]Cosima[/name] here. Such a beautiful name.
I really, really like both! Although the [name]Thea[/name] spelling is more familiar, I looked at the Nameberry entry for [name]Theia[/name] and think its background is very interesting (I love Greek mythology!).
I think, if you truly love both, maybe it would help you to consider which name you choose based on the baby’s temperament. [name]Theia[/name] has more of a demure, sweet feel to me, whereas [name]Cosima[/name] seems to lean more feisty and spunky. [name]Both[/name] are very good, but there is a chance that one would definitely suit your daughter more.
And don’t worry about a different feel to them, I actually could see them as a sibset! I don’t think the styles are far apart at all.
You really couldn’t go wrong here, in my opinion. My preferences make me lean towards [name]Cosima[/name], but maybe consider letting the personality of your child determine your course of action. 
Thanks so much for all of the advice everyone! I lean towards the theia spelling because I’m a sucker for Greek mythology but ill definitely take the [name]Thea[/name] spelling into consideration when making the final decision
Another vote for [name]Cosima[/name] here! I fell in love with it after hearing it on Orphan [name]Black[/name]; it’s such a beautiful name!
I love [name]Theia[/name]!
I vote for [name]Cosima[/name], but [name]Theia[/name] is OK. [name]Cosima[/name] is way better, thou.