visa/immigration query

My aunt (from Egypt) got married to a British citizen and moved to the UK in 2021, on what I believe to be a family/spouse visa. Her husband recently got sick and so hasn't been able to help her with the whole visa renewal process (which is due to expire within the next couple of months). As a result, she has asked me to help, but I don't know a thing about immigration/visas. If someone could explain the whole process, costs, names of visas and stuff (like what on earth is leave to remain?) that would be swell. Cheers