The pain from the burns on her arms lingered for days, both physically and emotionally, as a grim reminder of Alastor's cruelty and Sirius's forced obedience. Every time Saoirse looked at her arms, she was reminded of the moment she and Sirius had been bound by blood and servitude, a connection neither of them had chosen but could not escape.
Another thing she noticed though was Sirius felt her pain. He would constantly be rubbing his forearms and wore long sleeves to hide it from her, but she realized that this was just another way for Alastor to control his son. Sirius was actually such a gentle soul. She couldn't understand how he was related to such an evil king such as Alastor.
True to their promise, Saoirse and Sirius converted their relationship of prince and servant into a relationship of quiet rebellion and love. Everything that Saoirse had to do to serve him, was really just a way for her to encourage him to continue being the sweet boy he was and not be tainted by his father's endless lessons on malice and dark magic.
When Alastor became king, he established a school where vampires honed their power and so as expected of him, Sirius buried himself in his studies.
Shape-shifting like Sirius's was rare and so much of his discovery of his unique abilities was discovered by him and Saoirse by accident.
What Sirius had done that day when he burned her, that was a form of servant bond where he would always be able to find her if she ran off. When she was close, he could sense it. It was something only a person with noble blood was allowed to do, and it signified him as a family leader.
Secondly, he had learned about various marks that he could do with his fangs that would establish a sort of bond like he had done when he bit her.
This biting of him to her and her to him was establishing her as his mate. He would marry her eventually, but with their betrothal the bond was set where he would feel her physical and emotional pain. She could feel his physical pain.
From now on, if he was cut, she would be cut. If she felt hurt, he would feel hurt, and even if she felt hungry he would feel her hunger. As a family leader, he would be able to make sure that she was safe and cared for and she would in turn show loyalty to him.
When they married, they would complete the next step of their blood bond, which Sirius learned about too. He decided not to tell Saoirse about that.
Saoirse didn't go to school. She was put to work in the castle. She could become a wolf, and eventually learned she was a subspecies of vampire called a Lycanpire, a sort of in between ghost who could only be seen by the undead until she learned to control it.
Before she was thrown into the world of the vampires, she heard that there was magic that Fenrir established with the werewolves, but they had different abilities and nothing Sirius learned in school was something she was able to replicate. Alastor forbade interactions with the living, leaving Saoirse disconnected from her werewolf past.