Potential animal hoarding/neglect, not sure what to do

Location: California

My main question here is whether this may be an illegal situation, and if so, what I can do about it.

For some backstory, I took horseback riding lessons with the same instructor (who I’ll call F) from the ages of about 10-17. I’m now 20 and I’m visiting home for the last time before my family moves out of state, and stopped by the barn to visit my friends there and hang out with the animals. Over the past few years I’ve had an inkling that the business was not being run very well, but it all came to a head when I had a conversation with one of my friends from the barn yesterday where I realized I’m not the only one who sees the issues going on here.

The barn is a fairly big property with maybe 10 horses owned by F, as well as a ton of chickens, bunnies, a chihuahua, a couple of betta fish, and recently 2 baby goats and 2 kittens. The thing is, not all these animals appear to be properly cared for. Here’s where I’ll admit I don’t know much about animal care and could be wrong about some of this, some of the things I’ll point out may not be a big deal at all.
- the bunnies are kept in an empty horse stall. Female ones are free to roam the stall and male ones are kept in cages inside the stall so they don’t breed. They are however deliberately bred sometimes and I’m not sure why. As far as I know, F doesn’t sell the bunnies, I know she occasionally cooks and eats them with her family but that’s it. The bottom of the stall is covered in bunny poop. There’s a solid amount of space but there were about 8-9 roaming bunnies and a lot of the space was taken up by cages.
- the kittens were “rescued” from outside, there is a stray cat problem in the area but F has taken it upon herself to take in the kittens. They’re being kept in a cage, which to be fair is heated and has a litter box and stuff but I believe they would be much better cared for at an actual rescue like the SPCA.
- there is another stray cat, though not a kitten, being kept in a cage instead of being at a rescue or shelter where it has space or at least a chance at a real home.
- a couple years or so ago, she took in an orphaned baby possum. The possum now lives in a cage and as far as I know, is rarely interacted with or anything.
- the horses are well cared for as far as I know, except for one of them who has been “for sale” for like 2 years now but with no ad officially posted, so this horse hardly gets any exercise and appears to be in a paddock 24/7.
- the dog is kept in a pretty small room the vast majority of the day and only let out briefly a couple times a day to pee. There used to be 3 dogs until very recently (ended up in other homes) and they were all in that room and would very often pee on the floor.

I looked up to F a lot as a kid but now as an adult, I’m pretty disgusted by the whole operation. I don’t know what my options are or if I should do anything at all.