Though I don't feel terribly competent to answer your question, I still have an opinion, LOL. In a nutshell, my opinion is that your eldest may well have some sort of special needs but that it's too early to decide there is a problem and try to diagnose it.
I have an NT teenager who was a "late bloomer" with reading and writing - but you wouldn't know it now. Trying to find out what was "wrong" with her would have undermined her faith in herself. For her, the answer was to wait, and not to push the things she wasn't ready for.
My younger child is seven and has a metabolic disease which affects brain development, so it is almost certain that her quirks will turn out to be longer-lasting challenges rather than just her being a late bloomer. Nevertheless, I don't feel that the clock is ticking with respect to finding out exactly what she finds difficult and how best to help her. For her too, the answer (I feel) is to wait, to refrain from pressing her to do things she isn't yet inclined to do, and to watch her personality and abilities unfold. There are early clues - the short attention span, the resistance to tasks initiated by others, the late understanding of basic mathematical ideas - but they are only early clues. She's growing and changing, developing new skills and experiencing new environments. The full picture isn't here yet.
No doubt there are various specific conditions which have crossed your mind - "could my daughter have this?" I can't tell you not to worry; parents do worry about whether their children will have a rough time in life and whether we can do anything to smooth the path for them. However, outside of a school environment, does it matter if any conditions which your daughter may have are left undiagnosed for a few years longer? In most cases, I should think not.
To me, the absolutely essential question is, "Is my child feeling frustrated by the situation?" If she wants desperately to read and can't get the hang of it, if she is terribly lonely because her attempts to make and keep friends are awkward, if she wants to complete a task of her own choosing and gets distracted and wishes that she could finish it... then it will be time to investigate.
If none of that applies, then maybe it's more helpful to adjust your expectations and the way you are approaching things. Does your daughter actually need to read now, or do projects, or have friends of her own age? Mine doesn't need or want any of those things, not yet anyway.
From a school-centric point of view, seven looks quite old. Our girls would have finished three years of school by now. Teachers and parents would have been tearing their hair out for some time over why they hadn't advanced by the expected number of sub-levels. A diagnosis would be wanted so that this lack of progress doesn't have to look like the school's fault, and so the child doesn't have to suffer the daily discomfort of watching most everyone else in the class do things which she can't manage.
But being outside the system, we don't have to take that view. To me, seven is really young. I've known lots of HE children who were socially awkward and unable to read at seven. Some of them later turned out to be very ordinary people and some did not. It's hard to predict the future of each child. Perhaps it's best for their self-esteem if we just give them the space they need to grow in their own time, for a bit longer at least.