What about the end of The Joker or The house that Jack built? That’s not just relief or gratefulness..

Yes - those are definitely times when she shows how much he means to her. 

I think she just shows her affection differently, she is more tactile and ‘invades’ his personal space all the time. I don’t think her feelings are any less intense, perhaps she is a more cautious at first though…

So good...

I’ve given some thought to what you say and yes I’ve always thought she loved Steed but I’m unsure as to the depth of her feelings. Jealousy is such a destructive emotion and it’s so easy to become consumed by it. I don’t understand why she would secretly like to make him jealous and not for the first time either. I think she could risk undermining her relationship, a dangerous game. Perhaps she gets platonic vibes from Beresford but I don’t…said with hindsight perhaps.

I’m not certain why the depth of her feelings would be in question, any more than the depth of his feelings are in question when he flirts with Julie in Death at Bargain Prices. I really don’t get why her feelings would be suspect, given all the evidence there is to the contrary. 

To clarify, I don’t think that Emma is setting out with the goal of making Steed jealous - and I don’t really think that she’s aware that he is until at least after this scene (she seems completely genuine in her confusion about why he doesn’t like Beresford). But I think there’s a little pleasure in it, because his jealousy indicates the depth of his feeling towards her. Does she stoke it a little too much? Yes, and I think that’s a failing in her understanding of his feelings and of Beresford’s, not a desire to make Steed truly feel threatened.

I don’t mean that she thinks Beresford is totally platonic - but she wants his friendship. As @sparklywaistcoat has pointed out before, Emma doesn’t seem to have many friends and Beresford is intelligent, likable, gracious, and has similar interests. She can’t be held responsible for his attentions - she wants to be his friend, and as it becomes clearer that he’s not willing to stop there, she tries to extricate herself from the situation. All of that is pretty common in male/female relationships, and Emma complicates it by enjoying the fact that this attractive, intelligent man keeps complimenting her. It might be a failing to be susceptible to flattery, but it’s a very human failing. None of that equates to her not caring enough about Steed.