Different meanings of ですが


I have started reading 「魔女の宅急便」, and I found a sentence I quite understand,
but for the exact meaning of 「ですが」:

> キキのばあいも、十歳の中ごろ、魔女になる決心をしたの **ですが** 、そのあとすぐ、コキリさんの持っている魔法を習いはじめました

As far as I know, 「ですが」 means something like "but", and on
[Jisho](https://jisho.org/search/%E3%81%A7%E3%81%99%E3%81%8C) is listed as
such; as far as I understand,
[Weblio](https://www.weblio.jp/content/%E3%81%A7%E3%81%99%E3%81%8C) agrees.

With that meaning, I would translate the sentence something like "Kiki too,
when she was ten years old, decided to become a witch, **but** immediately
after that she started to learn the magic Kokiri [Kiki's mother] knew"
(literally, "have", but in English maybe "know" is a better fit).

Now, in the book girls deciding if they will be witches when they are 10 years
old, and if so starting training, is the norm; my doubt is that if I were to
write the same sentence in English, I'd write something on the line of "she
decide to become a witch, **so** immediately after", since it's a quite
logical consequence of her decision. I don't understand why 「ですが」 is used,
since if I were to translate it "but" in English it would give a meaning of
something unexpected, in some way contrary to the premise (e.g., "she decided
**not** to become a which, but she started training all the same": in this
case, the training would not be the logical consequence of her choice).

So, I was wondering what's the implication and/or reason to use 「ですが」 in this
sentence.

