My friend is getting worryingly close to my girlfriend

There are people that decide to become your relationship advisors even without you asking them, without you even being aware that you need relationship advice, or even that your relationship is in a state where people have to volunteer to ‘save’ it from collapse. And all along, you thought all was well between you and your girl.
I was not even that much friends with Sam. But Sam believed he knew what was best for Lydia and I because ‘that’s what friends do, they look out for their friends’.
This man pointed out to me that Lydia was not a happy woman. Yes, I told him Lydia was not happy. We had had a small disagreement, but there was nothing to worry about. I was not happy myself, we were working on it. Immediately, he told me “there is nothing small in a relationship, you should take every little thing seriously”.

Of course he was right, and of course I was not overlooking anything. It was as if my admission of this disturbance gave him a point to launch a full-fledged investigation into our relationship. I started seeing more of the guy, he would call me up just to see how I was doing, come visiting, things that really close friends do, which he wasn’t. I didn’t really mind him.
But then I learnt that he was doing the same thing with Lydia, probably on a bigger scale. Now, him and Lydia had been friends before I started out with her, but this was something different.
I learnt that he spent an incredible amount of time with her, and all they would do is just talk. Talk about what? I asked him, and he shrugged it off as, ‘you know, just being there for her in this rough period’.

I was alarmed! Since when did things get that serious to be termed as ‘rough’! My worry escalated when I found out what they talk about. He was telling her how to ‘handle’ better our relationship. Giving her relationship advice from the perspective of someone who knows her very well thus is in position to know what’s best for her. She told me what Sam was telling her about me, about us, and how we should move on. Frankly, I think the guy was making things worse; Lydia now seemed depressed.
It was like the whole relationship was now a big challenge that she needed to unravel, at least according to Sam, and there was danger looming.

So she worried that we might not survive our difficult moment. And yet our difficult moment was nothing more than a small disagreement we had had about her work.
Her boss made her work all the time, including most weekends, doing work that was at times not even hers. She said she didn’t really mind, but I did.
I thought she was letting the boss (it was a woman) take advantage of her. And because she was always working, we were not able to do things together. This disagreement had come because we had had to cancel a long standing engagement since her boss had called her in that very morning.

The disagreement had got heated up, but she had accepted to talk to the woman about it when the right time came. So, Sam had blown this way out of proportion that it looked like our whole relationship would crumble just because she took home some extra work.
When I told her to stop listening to Sam, he somehow got her listening again and told her that is how the end usually starts; me shutting her off from her ‘trusted’ friends, isolating her.