That woman will never get over her fear if she stays inside all the time. However, if she continues to go out and (hopefully) doesn't become ill, perhaps the repeated effort will make her feel that it isn't as terrifying as it was the first day she set foot out of her front door.
DP works with a lot of older colleagues (as in priority group ages). Whilst they are still very careful about masks and gloves and eye protection and face shields and distancing, etc, etc, they're now - because they have had no choice but to come to work - beginning to see, because they've been interacting with people/leaving the house for work and nothing bad has happened to them, that, combined with their priority vaccinations coming up, that they can be less on high alert at all times.
The general chit chat around him at work is largely what vaccine they want to have and where they'd like to go on holiday first once they've had them - but it's better than the shouting at clients to keep back, making up their own rules, sharing rumours about the Chinese and immigrants and barking at him that he needs to clean the client area before they come out from behind their desks for a trip to the bathroom.
In short, she won't desensitise herself to being outside and around other people if she doesn't continue to challenge herself and, frankly, be brave in going out whilst still frightened.
I'm sure you know that, really.