I see from both your post and your reply to missdeli that she knows her alphabet and a couple of words she thinks are important, which says to me that she is learning literacy and will learn as she chooses to when it's important to her. It reminds me of a talk by a woman who was unschooled along with her siblings and she related a story about how they were a bit concerned that her youngest sister wasn't learning to read and write, while her parents didn't seem concerned. This girl had an interest in Barbie dolls, however, and she used to get her siblings to help her search for them and their accessories eBay. Eventually, they refused to keep helping her, so the only way she could continue with her passion was to get literate herself, so she did.

My suggestions would be to continue to surround her with the language and literacy and maybe see if you can add things in to her games which could encourage her with reading and writing around her. For example when she playing vets you could bring up the idea of woiting down the animal's information for the surgery's records. You could trace large letters with your fingers so she starts to see the movements associated with writing the letters. Could you create boards or posters where you can put up letters to feature each week and have pictures with their words next to them? This way it's on display where she can see it, but isn't feeling pushed on it, but you may still be to engage her. This way you can introduce letters in a way that she can start to see the different phonetic uses of them, which can change with the word.

With regards learning Spanish, I think your instincts are right in that immersion is the best way for her to pick it up at this age. Are there places other than school that she can go to where she can pick it up? If not, then it won't necessarily be a bad thing for her to experience school for a bit to immerse her in the language, just monitor how she takes to it. Some children thrive in that environment, others don't. My eldest was a little like your daughter. She was a real sponge for learning and new things and would love the start of school when it was exciting and there were lots of new things to learn and do. However, she'd then get bored with the repetition and I'd have a sobbing daughter who didn't want to go to school any more.

My experience with homeschooling, was that it was constantly changing and evolving in order to immerse them in subjects in a way that they would enjoy and respond to. They started out in the school system, so they had the basics of literacy, but my youngest was nearly put off reading and writing completely by the schooling approach, so I ended up dropping it completely and we made a deal that she would choose her own books to read and if she really didn't like them after the first page she could take them back to the library unread. It took a while before she read anything, probably more out of insistence on not liking reading, but eventually she decided she'd find a series of books she liked and for a long time only read them. She was 7 nearly 8 when this happened and doesn't even remember it now.

I'll leave you with two things that helped me as a homeschooling parent. One is that we all question ourselves and wonder if we're up to the job. The other is something I think you are already doing instinctively, but I'll draw your attention to it, and that is to just observe what she is taking on board. I guarantee you they take on board way more than you think and surprise you regularly.

Also remember that everyone has different strengths and interests and it's only schools that put the pressure on for all children to be good at everything. My eldest is a maths and science nerd, but never really got the hang of reading comprehension, so she only connects with literacy on its logical side; grammar, spelling etc.

I feel like @trucklife-family would be able to offer some insights here, having fully unschooled her girls and learnt how to step back and trust their instincts to learn themselves.