Dad finally found someone!

My parents split up nearly 5 years ago, after being together for nearly 28(?) years, my Mum was in a new relationship pretty soon after they split. She moved away rather quickly, and got remarried 2 years after they split (they will have been married 3 years in May). At some point before Christmas, my Dad bumped into someone outside one of the shops and got talking. Not long after that, he lost a very close family friend and shut himself off for a while. Recently he bumped into her again and they hit it off and went for coffee. They've met up for coffee a few times since, and he eventually gathered up the courage to ask her if she had a partner and she said she didn't. They are in the early stages of being together now, not sure if they've defined the relationship yet or not, and I haven't met her yet.

Now here's where things get complicated. She has a prescription for Methadone (fair enough, she's trying to get clean, and she seems to make my Dad happy). My Dad went to pick up my niece today, and his friend/girlfriend was in the car with him, my sister or her boyfriend got my niece in the car (not sure which) and then AFTER they drove away my sisters boyfriend told my sister that the person in the car with my Dad is a crackhead. So my sister phones ME up, to ask about it?? And freak out about how she wants her daughter back (keeping in mind that my sister has been trying to get anyone and everyone to babysit all week because she "can't deal with listening to her whine" - try taking her to the park then??) Not knowing about the methadone prescription at the time, I asked my sister how she knew or what made her think that. She says that apparently this woman is a friend of a friend of her boyfriends. I then hear her boyfriend (not her child's Dad) in the background say "no, she used to come to my house to buy it". I tell her I know nothing about it, and she needs to speak to Dad if she wants him to take her daughter back.

A few hours later, I get a call from my Dad. He explains what's happened, I tell him about the phone call I had with my sister. He nearly starts crying when he tells me that she makes him happy and asks me how I feel about it. I tell him that he can't put his happiness on hold for us kids and I know he'd never put us, or his grandchildren, in any danger. I told him that I wouldn't be leaving my children with her, but I wouldn't be doing that whether she was an ex addict or not. I said that it would be nice to meet her before my children do, but I'd do that with anyone. If she has a prescription for Methadone, it means she's working on getting clean.

Of course I'm going to be wary, I was of my Mum's new partner to start off with too. I'm more worried about my Dad getting hurt than this womans past. However, one of my problems is that my sisters boyfriend basically admitted to selling drugs and she doesn't have a problem with that whatsoever, but she has a problem with my Dads friend/girlfriend getting clean!?

I don't know. I just needed to put it somewhere to try to gather my thoughts and it's not really worked as well as I'd hoped... I don't even know if this is the right group.