Your feelings are not wrong, you know nobody's home . Often, if not most of the time, we "understand" others better than ourselves (and therefore envy them because they've "it" all figured out contrary to us), so no worry.

Go back to First Person when that feels better and more natural to you. I did so from the beginning – Laura and Vince would feel wrong to me in Third Person.

Go back to First Person and I bet Tamsin will "forgive" you and "come back".

Why "learn" Third at all when you don't want to?

We're made to resonate, means: people – no matter which person they prefer – will note when you feel uncomfortable and alien with your choice, and wonder why you do it. And that'll distract them from your story.

So, Miss A, don't fret and go back to what YOU want. You can care about the others later.