I have a close friend of 16 years and has a bf of 5 years I've only met once even though we live in London and see each other every 2 months, and Whatsapp a few times a week. We are part of a group of 4 very close friends + partners, and no one else has met him other than the 1 time either.
For background, she was in a long term relationship and we knew her ex very well, he attended events, she talked about him etc. She ended it but it was amicable as they grew apart. She then moved abroad, and met her current bf. At the start she talked about him loads, shared photos, updated on milestones (like him saying he loved her, meeting his parents etc). She would come back to London every few months, and we met him on his first trip back with her - only for 2 hours so not a long time. Lovely guy, we all really liked him and she said he did too. Over the next 2 years she'd come back with him regularly but we never met him again, which was understandable as they were doing touristy things around the UK. Still talked about him a lot.
She then decided to move back to London, and he was supposed to move with her. He dragged his feet as doesn't like London (is from Austria) but eventually agreed - this was 2+ years ago. In the 2+ years since he's moved here, we haven't met him at all. One of our group got married, gave us a lot of notice, but he didn't attend as was visiting friends back home. We've celebrated a few 40ths, he's missed them all as he's away. We have regular birthday and xmas catch ups - never attends. She complained when he first moved that he had no friends - he and my DH share a hobby so i suggested they could do it together, she loved the idea and said he'd be in touch. He never was. Another friend's DH invited him a few times to another shared hobby - he never replied, apparently he is bad at texting.
She has barely spoken about him in 2 years, and the last year not at all. Whenever I ask how he's doing, she'll say 'fine' and quickly change the subject. She talks about her future plans with no mention of him. Eg. she wants to take a sabbatical and travel the world - when i asked whether he would join, she seemed surprised i'd asked and shrugged and said he'd do a sabbatical too but not yet.
It's at a point where it just feels odd. She always asks about our relationships and is genuinely interested to discuss it, and is opinionated (not a bad thing) - but hers is a black box. She's a good friend so ultimately it doesn't matter, but she's always been honest about everything so unsure why she wouldn't tell us if they did break up? Or if they are together, why he never wants to meet us (did we offend him, but ~4 years is a long time to not say something?). It feels like this big gap between us and i'm not sure why. What would you make of it?