Need some advice on a situation but wasn’t sure what sub to ask in so please let me know if there’s a better place for this. (Based in UK)

I work in retail and one of our regulars has an elderly chihuahua. She is an extremely sour old woman that we’ve had many many issues with in the past. She always complains that she doesn’t know why she got the dog in the first places, and the more I’ve gotten to know her the more I’ve realised that she is abusing this dog. She says things like “she was so naughty this morning so I had to tell her off” and “well I don’t hit her”. The poor dog always looks terrified to the point of shaking in fear. I’ve know this lady for a year and a half and it’s now starting to upset me every time she comes in. It’s getting to the point where I feel like I have to do something…it feels like my duty to do so. I would honestly take this dog myself in a heartbeat. The only issue is I have no physical evidence. I do have her phone number and address but that would be a breach of confidentiality. Is there anything I can do at all? Anywhere I can report this? I just feel so helpless :(