Do you like it?
sorry I dont like it
I kind of like it, although I don’t love the “gus“ part especially in a girl’s name. It’s recognizable but has international flair, which I like. Other names you might like: Antonella, Isidora, Amalia, Josefina.
I'd prefer Angelina, Evangelina or katerina
It comes across like somebody just didn't know how to spell Augustina correctly. I would go with either Augustina or Agnes rather than try to combine. If you are aiming for the nickname Aggie, Augustina works perfectly well as long form of her name.
I do think that Agustina is a real variant with a legitimate history separate from Augustina... so although based on the languages I speak natively I'm more familiar with Augustina (and really love it!), I don't think Agustina looks wrong, either. I seem to remember that Agustina is Spanish, right? I think other languages also drop the u - like Italian is Agostina? By any spelling and in both masculine and feminine variants, I really like the Augustinus name family, and I have a particular fondness for -ina names, so the venn diagram overlap is a slam dunk for me. Nice stately name with lots of kicky nickname options for maximum versatility! And frankly, both spellings are so rare in the US (there were 16 Agustinas and 23 Augustinas last year) that I think you could safely pick the one that is most pleasing to you, in reflecting your heritage or just your asthetic preference.
If the spelling and name have a personal significance for you I think it's a viable option.
How are you pronouncing it? I will say that with my default guess at the spelling, the first two syllables sound just like the first two syllables in "agony" (and the first three syllables rhyme with it). I'm sure that association contributes to my discomfort with the name. With a tweaked pronunciation, especially if you live somewhere that you could easily enforce a different pronunciation, I would like it better.
Other things to consider: Especially with a four-syllable name, how do you feel about nicknames? Most likely options are Aggie, Gussie, and Tina--while you can generally pick one or none of these when she's small, children (and in-laws) are notorious for enforcing some other choice, so you probably want to be able to live with any of them. Similarly, how much will it bother you if she's mistaken for an Augustina or even Augusta? If you're in an English-speaking context I suspect you'll get these pretty often, just based on how much more common August- is as a name element in general. Name confusion doesn't need to be a deal-breaker, but again you want to think about whether you're the kind of person who will be able to just roll with it (and teach your daughter to roll with it) or if it will drive you absolutely bananas.