For #2 - I never have a set method for reading cards, I just use my imagination to get meanings about them. In this instance the subject is the relationship itself. So I looked at the cards speaking about how the relationship functions rather than labeling any card as X or Y person and divining from that. The first card is the High Priestess. She never speaks, just observes and connects with people using her intuition above all else. She knows a lot but doesn't reveal it all, ever. So maybe a more acute interpretation of this card regarding your question is they feel the relationship with Person A has undertones and hidden meanings to it, because the High Priestess is all about non-verbal cues, she/ they doesn't communicate head on. But I saw this card as "privacy" first, so...
Next The Emperor: He's beside the High Priestess and his personality is that of a stubborn mule, but he defends what's his. Who's behind him? The High Priestess. Not to mention their colors are sort of opposite - blue = cold, red = hot (in the Rider-Waite anyway, which is what I always refer to in my head out of habit. OH! Maybe B feels the relationship could go either way and is hot or cold? See, my mind goes in all different directions depending on the day.) He's also in the middle. So whatever is coming in from the 3 of Wands, he will see first before he shares it with the High Priestess, who although clever, is kind of in the dark if she can't see over the Emperor.
Finally, the 3 of Wands. Onlookers. People observing the High Priestess and Emperor from afar as well as indicating the relationship is open at this point and reaching a peak decision making stage before achieving any kind of stability (that they're striving for in the 4 of Wands.)
Now, to conclude all of this - it's about how B sees the relationship itself. If we make the High Priestess the significator for the relationship then B would be the Emperor in between other people (3 of Wands) and her (HP.) << Wow, I could've just said that and saved you a lot of time. I ramble when I'm tired!
For #1- I meant person A will know everything how B feels about the relationship. The Magician will reveal what he uses for all his tricks (again referring to Rider-Waite) so the games or the "waiting game" (2 of Pentacles + 7 of Pentacles) will stop. The Magician's energy kind of reminds me of The Sun but with more details.