Hatred by daughter
Dear glimmer of light. To give you some peace of mind. I would suggest you BE there when your daughter comes. She doesn't have to know you're there, tell your other daughter to not tell her you're going to be there. It's a bluff that your daughter says she will involve the police if she doesn't get her stuff back. If she did ring the police to say her stuff was stolen, they would ask all sorts of questions. She would have to prove you took them, if she left them there when she left, how could you take them? Sorry to say this, she's behaving like a spoilt brat. Just be there when she comes, it's your home, she actually needs your permission now to get in. If she comes in while you're not there, without your permission, she's violating you. Your other daughter can't let her in without your permission. Tell your daughter to ring and make arrangements, at your convenience, to come and get her stuff. If she rings the police, that'll be one thing they'll query.
Stand your ground on this one. Your daughter needs to know, your home is your home, the same as her home is her home. Who you let in or not is at your discretion.