First and most important thing: she is seven weeks old
. She is not even physically capable of being house broken at this age. She should not even be away from her breeder. I know the situation that landed her in your care, but believe me when I say that expecting anything whatsoever from her at this age is expecting way too much. If your other pup is catching on (I think I remember one being about two weeks older, but can't recall which is which), I would chalk that up to age or luck.
1. Don't wait for her to start sniffing. Take her out after every time she eats, drinks, plays, or wakes up, plus every 20-30 minutes, or obviously if she seems about to go (sniffing, etc.). With my boy we would set a timer. When the timer went off the dog went outside and stayed outside until he pottied, then we'd come inside and restart the timer. Regardless of where the timer was at we'd also always go outside right after coming out of the crate and after eating.
2. What I have always done is for the first few weeks, playing is indoors only. They will still want to run around and engage with you outside, but don't do it. Just wait her out. If you're outside for an hour, you're outside for an hour. When she goes, praise, reward, and immediately inside. Personally, I don't even wait for them to pee if they've only pooped or vice versa for a couple weeks, because I've found it effective to make the connection for them that going potty = going back inside, especially in the winter. I've found that it clicks a little sooner if going inside immediately follows going potty. If she still needs to do one or the other, well...you'll be out again within 15 minutes, anyway. When she goes, squat down so that she will run to you, pets and praise, pick her up and inside. WHat I did is didn't allow ANY play outside until my dog did his business. I'd sit and wait and be the most boring person ever and then, once he pee'd/poo'd/both I would praise him and tell him that he was good and then we'd play. Now, when he runs outside the first thing he does is potty and then he runs around like a maniac.
3. A 7 week old pooping in her crate is really not surprising, but how big is her crate? If it's so big that she feels like she can poop and easily get away from it, it's more likely to happen. A puppy being crate trained should have just enough room to be comfortable in there. If this is an issue, check out crate dividers - very handy. I agree.
4. As for making her comfortable in there - Crate Training
has some good information about crate games and crate training. At 7 weeks, though, again...normal. Most of it is simply a matter of patience.
5. Give her some time. It is really, really unreasonable to expect any puppy to even approach house-broken before 10-12 weeks, and there are many, many dogs still working on it at 16 or so. 7 weeks is way, way too soon to have any expectations. I don't give these pointers in the spirit of "this might help you fix your problem," because right now (as far as house-breaking goes, anyway...) there is not a problem. I give these pointers only in the "general guidelines for how to do it" sense. Good luck.