Honey
really hard situation you've got here, I'd be really careful,yes it's sad that there will b a baby, but u have to consider.

Is C's mum still on drugs and how far into the pregnancy did she do it for?
If it turns out to be C's father is the dad, then won't he want it?
What if you fall in love with baby and all turns out for the best then she tells you 5 yrs down the track that she's drug free and has leagal rights as she's the mother?

Don't mean to be mean or sound like a *****, but maybe your hearts ruling your head. If I'm wrong then sorry I don't mean to offend you at all, and Im very sorry.