Bubble query

I live in Northern Ireland and have a query about whether or not my 68 year old sister is in my bubble. She suffers from depression and lives on her own in a different town, but moved in with my brother at the start of the pandemic. She moved back home again in July, when things eased, and then came down and stayed with myself and wife (who’s disabled) for 2 weeks.
She is wanting to come down again in November for a few days, and I am not sure now if we are part of her bubble or not.
Could anyone on here answer this or advise me on where I could email this query to for an answer.