'bij' both denotes physical proximity (he is close to her, sitting next to her) as well as 'at her place'. 'Hij is met haar' feels more as an active process; 'hij is met haar naar de film' -> he is with her to the movies. 'met haar' can also be used as 'in a relationship with her' or 'going out with her', something that you can't say with 'bij haar'.
Okay so, 'bij' is used when, for example I'm with someone right now and he/she is next to me at this very moment, while 'met' is used when if for example I want to say I'm going to the movies with him/her later, or I'm not with that person to the place I am now but that person will be with me soon?
Am I understanding it right? If not, please correct me, thank you.
this word "bij" has several translations into English, in one case "by" was the only way of normal translation into English, just like now, the most normal meaning of this preposition in this clause is with. Of course, "by her" translated to one's native language may make sense but not vice versa