Betta Fish: New Betta parent help

Can I please get some help in what might be going on with her and how I can help, please?

I picked up this female betta yesterday. The shop assistant mentioned she may be pregnant as she's round. I didn't think much of it at the time because she was on her own so assuming they can't be fertile eggs nothing to worry about. Now I've woken up worried that it could be something else or the stress of the environment change could be dangerous.

It looks like an egg in the video but is her roundness ok? My research so far has led to advice of not to feed her but what if she's hungry? Will she starve? Is she happy?

Additional info:

This is my first fish – for the last 3-4 months I've been growing aquatic plants and tending to hitchhiker snails and copepods. My tank has been cycled for a few months so introduced this Betta.

She is spritely and curious of me when I come up to the tank. This afternoon I found her hiding in the shrimp caves (no shrimps) so I've closed the blinds and added cardboard to the back of the tank for more darkness – this helped and she's back in the main areas. There is established driftwood in the tank so the water is a little dark but it has lightened up a lot over the months so I'm currently brewing some oak leaf tea to try and darken her water.

She is in the tank on her own except the copepods and bladder/ramshon snails. When I first put her in last night she bit a snail (so fiesty) but has since started ignoring them all.

The tank is 20L (I think that's 5 gallons). There are aquatic plants and I have an established Pothos growing out of the water and some small golden palm. Substrate is aquasoil capped with freshwater aquarium sand and stone (adding this context as I think people may ask).

Tank is heated currently at 24.7 degrees Celcius (76.5 F)