Krdytkyu

One of the characters in my book feels the need to protect a woman she barely knows and later on it will be revealed that they have a magical which causes the character in question to want to protect the woman regardless of what their relationship is. I don't want to just say 'It was almost magical' or something similar as to not to reveal the plot twist but i fear that if i don't indicate towards something the audience will think of the protection as the author forcing them together.

What can i do in order to indicate something is afoot without actually revealing the bond?

The basic setting is

1)Medieval High Fantasy

2)The protected character is a noble.

3)The protector is one of the servants.

4)Neither of them had any conversation beyond 'I brought you your X milady.

Mirror addiction. Addiction is very much a compulsive behavior. Often times feeding that addiction is fun and exactly what the person wants. And often times it is unpleasant with significant repercussions and people wish more than anything they didn't need it.

So one way to convey that is to have the character engaging in the compulsive behavior even when it is detrimental to them, but also when they are indicating that they don't want to.

Another way to indicate the behavior is compulsive is to have them try to stop (maybe repeatedly) unsuccessfully, possibly with physical and/or mental repercussions.

Diana Wynne Jones did this (quite well) in The Merlin Conspiracy. The reveal, near the end of the story, was quite effective.

I would challenge the idea that you need to hint directly to your audience why a servant feels a particular compulsion to protect her mistress (or her master's child, or whatever connection there is). Rather, have your protector-character rationalize her extraordinary actions to herself. ("This is my duty as a servant. Sure, I'm not normally big on duty, but... She just couldn't make it without me.") The more obviously false the rationalizations, the less unnatural it will seem to the reader when it turns out there was a magical compulsion in play. ("Okay, she stepped up and solved that problem without me, but I'm SURE she needs my help most of the time; she's high-born and can't handle things like...")

People in general often act first and then explain to themselves why they are doing what they're doing - attempting to impose reasonable motives on possibly unreasonable behavior. Interesting story tensions arise when it becomes difficult or impossible for a character to maintain their false self-narrative regarding their behavior.