Communication skills are key here. She may be able to understand English and might be able to speak it at a functional level, enough to do her job but if she does have a strong accent that people cannot understand then it will hold her back, both in her career and at a social level.
I too would recommend voice training or what we used to call elocution lessons to help soften her accent. Also English classes. That would probably be enough for starters. Also the family taking her out and about as much as possible, covid permitting obviously.
Simply advising her to join groups won't really help. It's bad enough for quiet shy people to join groups of strangers let alone someone with language issues.
I also think that you mustn't minimise cultural differences, religious teachings etc Some cultures do take a very dim view of LBQT issues.. We Brits are very tolerant on such matters, not all other countries are.
We might think it wrong and narrow minded but she can't help the way she was brought up. Hopefully as she becomes more integrated in British Society she will become more tolerant and open minded.
A lot of her reticence to integrate with those of different racial, cultural backgrounds will be due to fear and nervousness. The only way round it is education. As she integrates and assimilates into the British way of life she will begin to broaden her mind.
But she needs help.
How much do you know about her culture, her history, her family. Encourage her to talk about herself and get her to open up. That way it will be easier to learn "what floats her boat" and find activities, groups etc she can join. But not yet, she's not ready,
Right now just joining any old group, hoping something might stick is not the best way forward. Top priority is for her to improve her communication skills. Until that happens she will just feel isolated and lonely.
My mother came to the U.K. in 1949 as a war bride with not a word of English. She lived in the Black Country at first. She taught herself English, there were no classes available. She spoke perfect English, with just a slice trace of her home accent, none of the Black Country.
I asked her how come she spoke such good English without any trace of a Black Country accent. She said she copied the people on the BBC because she figured they would be the best speakers so she did her best to emulate them,
It might sound snobby to suggest elocution lessons but trust me she won't end up sounding too "plummy". I took them as a child to help me overcome a stutter and although I'm often told I have a nice speaking voice, I don not, want of a better word, come over as too posh or plummy. My speech is just clear and easily understood, which is what she needs to aim for.