Hello everyone. Long time lurker first time poster here. I decided to join up after something that has been going on for a couple of months.
Background > I got my DD a bunny for her 10th birthday July 2017 (before I get bashed for giving a child a pet as a gift, she had been wanting one for YEARS and we did immense research. She is a rabbit expert and little rabbit is cared for great)
And since then the NDNs child and my DDs friend had been asking for one and eventually in around May/June this year they got her one. It was a rescue I think as it wasn't a baby. I've been great friends with the neighbour since I moved here when my DDs were only babies and they've been best friends with little girl next door since (who is 9 now, my DDs are 10 and 11).
But I've noticed the rabbit isnt looked after as much, basically neglected. NDN is not very strict and if I'm being honest would rather give her children what they want to shut them up. She did ask about how to care for a rabbit beforehand so I thought they'd be great owners but she isnt invested in the rabbit that much. Ours is an indoor rabbit and NDN decided against that so I said it would have to have a hutch to live in and then just recently I found out that they'd been keeping it inside their playhouse. It's a massive wooden thing with two stories and was built for their teenage daughter when she was a child but obviously my DDs friend has it now. At first I thought they'd placed the hutch inside the playhouse until I went round just a couple of weeks ago to see the rabbit to find hay just sprawled about the floor with his food bowl and a cushion. It must be freezing now in winter I felt sorry for the rabbit.
There have been incidents since then with their Yorkshire terrier chasing him around the garden and he has gotten out a few times through their side gate and into the front but theyve managed to catch him until just a week ago when he got out again and they'd had to chasing him up the road and I'd helped until we finally caught him. Poor thing was so shaken up I'd offered to help calm him down but NDN just said put him back into the playhouse alone.
Now DD2 recently just a few days confided in me that an older girl around 13 and her younger sister joined the girls inside the playhouse and had a hold of the NDN rabbit holding him up by his ears and legs upside down. Oh god I was nearly sick imagining it and DD was distraught as she has a cat herself and plays with her sister's rabbit and that older girl has bullied her before because she has Asperger's so she was too timid to stand up and I imagine my DD1 was as well.
My DH has told me to leave it and mind our own business but I can't knowing a poor animal is being neglected and abused right next door. 
Should I call the RSPCA? I know bringing it up will just send NDN into defensive mode. They used to have a hamster but it escaped under the playhouse and never came out.