@Shaz51 sitting with you in those feelings; they are valid and very understandable feelings.
Did it feel good to be able to send that message to your cousin?
I think that was a tactful way of commenting that you saw she was in town, and would have liked to see her. 😊 Do you think they will have the time to catch up with you whilst they are nearby, knowing that you would like to see them? (Or was she leaving town when you saw her, rather than arriving for the upcoming week?)
It sounds like your mum was a bit like the "glue" between the relatives?
Was there something that you can think of that your mum used to do that brought the family together? (a topic everyone would get involved in discussing? an annual lunch/dinner event?)
Does your family have any online group-chat to keep in contact via?
My relatives on my mum's side that live local to me, we meet for dinner once a month (whoever is available) and have a chat-group to tell people what date & who's turn it is to host, and to RSVP. My sister, father, mother and I (even though my parents are split) still have a "family chat" group which we occasionally share photos or articles in - we don't use it often, but it can be a good way to keep in contact for big updates (e.g. my sister is in the process of having a house built, so she sends us photo updates occasionally). I wonder if that could be a way to stay a little more connected to them?