I…can’t speak to what its usage is like in Greek. But in English, it does look a little like someone wanted to make a trendy combination of Abigail and Gaia. It looks unusual, and potentially incongruous, because Abigail is biblical and Gaia is associated with “New Agey-ness”. Personally not a fan of Abigail due to the sound, so I appreciate why someone would use an alternate form.
This name sounds so regal and gorgeous, plus I can think of several cute nicknames to go with it. I love Abigail, but I will always slightly prefer Abigaia, for its enhanced beauty.
Abigail is a solid name. However, Abigaia sounds cooler. Also, in the English Speaking world, how many Abigail's do you know? I bet you know more of them than Abigaia's.