hi E.,
That's great that she is doing well with #1 - my daughter took longer, and we also had the same difficulties with #2. I agree with the other poster here who mentioned they are 'attached' to it (gross, but true).
Does she have her own little potty chair? This is often more comfortable for them to sit on for the longer period of time to go #2.
I explained to her that if she did #2 in the potty chair instead of the diaper, it wasn't all squished together and she could dump it into the big potty herself and say 'bye bye' to it when we flushed. (yes she might miss a bit, be ready with the antiseptic wipes). We also bought some special new books that we kept in the bathroom - and I would read to her while she was sitting on her potty. :-)
I believe it is very important not to rush this kind of thing, and never scold or punish over it (despite the advice you'll get) - it has psychological impact.
good luck!