Feeling of can't breathe when indoors for long time? (post Covid)

This is a strange one that we don’t even mention to doctors, because it feels a bit weird.

When my mother goes into a large supermarket and stays for about 15 minutes, she starts to feel like she’s suffocating, especially if she’s deep inside the store. She says she needs to get out to breathe properly. It feels very congested to her.

She said that if she is nearer to the entrance, then she can stay there much longer.

Interestingly, she’s fine in smaller shops that aren’t as deep. She was fine is say large buildings, like hospitals, without any issues.

She’s even okay in lifts, although those rides are usually short anyway.

It’s almost like she can’t stay in certain large, enclosed spaces for too long. She starts to feel like she’s suffocating. At home, though, she feels completely fine indoors. In the car, she said she can open the window.

When she had Covid, she experienced brain fog (which has improved over time) and vertigo when riding in a car. We’re not sure if the vertigo was caused by Covid or a fall she had, during which she lost consciousness.

These supermarket episodes started after she had Covid. We’re unsure if they began right after the illness or after she received the vaccine post-Covid (taken about 2 months later).

I don't know if there are others?