Care over Christmas

I am currently in tier 4 and was supposed to have my mother who is a vulnerable pensioner for Christmas day and boxing day, My sister is her main carer and I was giving her respite for them days, I have looked at the direct gov rules but am all confused by them, Can I still have my mother come to me for them few days, she lives in a communal building for over 55s? Also we are all in tier 4, We are clear from covid me and my household as a test has been done?

This comes from Government advice to those who are considered vulnerable, link to the full page below.

You may not form a Christmas bubble if you live in a Tier 4 area. You are still allowed to meet with your support bubble.