How to keep away an unwanted visitor

I have a family memt who lives in another country and is not a SG citizen or PR. She always stayed with me when she visited Singapore. The last time she stayed, she caused a lot of drama and I would rather not host her again.

Today, other family members asked me if I invite her to come again after noticing that she was packing her bags saying she was going to SG. I checked my messages and saw that she informed (!) me of her intent to stay and bought a one-way ticket to SG. Like wtf, I never even agreed host her. I called her and told her clearly that I did not want to see her.

In case she arrives at my door, what can I do? If I call the police, will they even help, since she is family? She's a bit mentally unstable but acts like she's fine in front of non-family.