Inconsistent potty user - advice?

[Weareboatsremember]

Dd is 23 months and has been using the potty for wees and poos for about 5 months before and after naps, and at other times of the day too, but only if I put her on it.
Sometimes she will ask for the potty, but will then only do a tiny wee. She knows that she is pooing, and will run up to me as soon as she has done it in her nappy and tell me.
I've swapped over to pull-ups for ease of using the potty, and tried a sticker chart today, but it didn't seem to make her any better at asking for the potty. If I ask her if she needs to use the potty she says "no thank you mommy", but if I put her on it then she'll do a decent sized wee!
I'm just looking for advice on where to go from here. Ideally I'd like her out of nappies by the end of the summer!