My sisters anxiety is worrying me and my parents

I think my younger sister is suffering with anxiety (mainly health related but other things too) and recently it has got so much worse (especially since the uk lockdown started). She basically worries about every little thing that might be wrong with her and constantly seeks reassurance from my mum by bombarding her with repetative questions that usually follow the same format or sequence. Yesterday she asked the same thing 9 times in 4 hours and was questioning everything for 2 hours before bed so much that none of us got to sleep until 1am. If you try to interrupt her while she is telling my mum these things then she shouts at you and speeds up her speaking. There is nothing I can do to ease the burden on my mum and I am really worried about my mum's physical and mental health.

About a month ago things seemed to be making an improvement as she got herself a volunteering job at our local food bank that seemed to be helping her. However due to the coronavirus crisis that had to stop and so she got worse.

She does want help but none of us really know how to get it for her since doctors surgeries are closed to face to face appointments and she doesn't want to do a telephone appointment as she has a fear of speaking to people on the phone. I also don't know how any mental health treatments like CBT or counselling are possible right now due to social distancing measures. As a household we simply cannot wait until this coronavirus is over as every day is getting so much worse.

Hi, I'm not sure if this will be helpful but what if you try introducing hobbies to your sister as a distraction. As you said your sister began to improve while volunteering, so try giving her something to do that will interest her without any pressure such as art or exercise. Hope your sister gets better.

Anxiety is very common among girls.
How old is your sister?
Does her anxiety affect her study?

She's 21, she finished college over a year ago. She had anxiety issues then, but college provided her with a focus. Since then it's been worse and since the coronavirus lockdown even more so.
She feels like she has to say every fear or thought she has out loud and if she doesn't it makes her upset. The rest of us in the house have our own worries at this time. I'm a key worker in a supermarket so I get scared most days going into work, I don't talk to my parents about it as they have enough to deal with in regards to my sister. I am able to talk to friends online though.

She already does a lot of art work as it's her main hobby that she hopes to turn into a career. She is okay when she is working on that, but she obviously can't do art work 24/7. It's in between and its only getting worse tbh. We are all at a loss as to what to do. We all try to be patient with her but there are only so much we can take as we're only human.
When we go on walks each day she will spend most of the time asking if the person we walked past was over 2m away, even though this is something she can see herself.