Disipline means "to teach". I think it's important to remember that considerate behaviour is something you teach. To punish your child for not yet knowing the social norms, or not yet having the control to follow them would not be appropriate teaching. Just remind her, but sometimes let it go. You can't reason with the unreasonable so giving a lecture in the middle of a meltdown wont be productive. I offer cuddles to help my son calm down then remind him what we are doing and continue on with it (ie. going in the pram to the car). You may need to cut your visits short as her attention span is short and you need to consider what is reasonable to expect of a 15 month old.

As for books I love:
Children are people too by Louise Porter- explains the perils of a rewards & punishments system and offers advice on how to guide your child's behaviour, develop their self esteem and also deal with specific situations eg. tantrum at the shops.

Toddler Tactics by Pinky McKay- a nice reminder of the world of toddler hood and what they are dealing with and what you can reasonably expect.

The secret of happy children by Steve Biddulph- actually I haven't read this but I recently went to the seminar on this book and I thought he had some good things to point out about how to deal with the toddler years and the importance of developing your child's sense of socially acceptable behaviour.

Hope that helps