Birthday Message

[Polly345]

My friend sent me a text to say she would be busy all day on my birthday and was saying Happy birthday in advance. She doesn't live nearby so most communication is by text..
Am i unreasonable to feel sad that she is too busy to send a text?

How in advance was this?

Well at least she remembered.

I've known my best friend for 30 years. Neither of us are capable of remembering the exact dates of each others birthday. It doesn't bother us because we demonstrate that we care at random times throughout the year ( saw this and thought of you, so I bought it for you).
We don't need to validate ourselves or our friendship by arbitary, supposedly celebratory, events.

YANBU, she should have just set a reminder to send a quick happy birthday.

Do you ever see her anymore? I would just stop the texting her on her birthday, remove any obligation on her part.

But she did text you happy birthday? It was early. She didn't forget, she just knew she might be too busy on your actual birthday day to remember to text or actually take time to text. She has a life and other things going on.

You don't know what she is doing. It's good that she has remembered to say now.
Is she travelling and chance that she will forget because she will be focusing on this?
Is there a possibility she is going into hospital and might forget because she is worried about an appointment/surgery?
Maybe she has a pet and they are ill and she has arranged for them to be put down that day?
There could be all sorts of explanations and maybe she doesn't want to say but is kind enough to remember to say now so you aren't wondering why she didn't message on the day.

Night before completely acceptable. a week before not so much

I find it hard to believe she would be so busy she wouldn't have time to send a two word message - " Happy Birthday" - on the actual day. It would take a few seconds.
It seems a very strange thing to tell you this and it's quite understandable you feel as though you are being told where you are in her list of priorities OP.
I'd actually have preferred her not to text on the birthday but to text it the next day with an apology that she'd been so busy it had slipped her mind. That would be much more natural and better than telling you in advance.