My father met a new woman after my mom's death, they're moving very fast. How do I make sure his assets are protected?

So my amazing mother unfortunately passed away from cancer this past May (on Mother's day). My dad who was completely devoted to her and an outstanding caregiver was lost without her and has now met a new woman.

I wasn't happy with how quickly he decided to do this but I'm trying to support him the best I can. This new lady seems genuine and she has her own money and (owns her own apartment).

My dad's will is updated and has his assets (RRSP's, TFSA and non-registered) investments split equally between my brother and I. His house is also fully paid off and he has that going to my brother and I as well. My dad has me as his executor and power of attorney.

Now this new woman is spending a lot of time at his place and he's spending time at hers. I have the following questions:

  1. If she moves in with him full time, is she entitled to any part of the house, seeing they'd be common law partners? Or would she have no claim to it since it's going to my brother and I in the will?

  2. Same goes about his savings and investments, is she entitled to any of that if they become common law partners?

I hate talking about this but my dad is extremely gullible and a giving person in general. He spends money and pays for everything. That's his right but I do have concerns with him getting carried away.

Prior to my mom passing, she figured something like this would happen and told both me and my brother that everything they worked for was for us and that to ensure my dad doesn't get swindled by another woman. She knows him and told him the same thing. She wants their money and and their house to go to us. It's not a huge inheritance by any means but it's significant and while my dad has a right to spend it the way he wants, I'm afraid of this woman trying to get it on it all.

They're in BC.

Any advice or further guidance would be very much appreciated. Thanks!