I think you and the others are right. Show her how to love her kids and treat them like a part of her. You said you already made one suggestion and she was open to it.
So she probably needs a mommy mentor to help her along.
Tell her things like proping a bottle in the baby's mouth can cause air bubbles and stomach aches. That leaving a bottle in their mouth for too long can lead to tooth root and she may have to get her teeth pulled by the time she turns 2 or 3
Shaking a baby can cause brain trauma and kill the kid.
Lashing out at your kid because you are in a mood is taking your anger out on the kid and can cause them to grow up disrespecting you.

Helpful hints may be all she needs.

Jennie,these are all good suggestions,but,you don't know this woman very well,and I would suggest you don't get to close until you know something more,the last thing you need is the kids and the mother hanging around your house everyday and the weekends as well.

I think you are spending too much time with the kids than their own mother so you are bound to bond more with them. Becareful of becoming a bit jealous without noticing. Not your fault though but you will be heart broken should she decide to completely remove the kids from your care. Try not to get too emotionally involved. You seem like a loving mother but it might kill your heart.

Yes I understand hiswill. I've been through that before, so I try not to get TOO attached. I had a ladie I was babysitting for, and I did for 3 months, her adorable 1 year old little boy who was just so sweet and such a joy to watch. I never really knew his mother well. But one day, (of course on the day she was suppose to pay me) I never heard from them again :( she didn't bring him over, didn't call, didn't answer my calls, nothing. It did break my heart. So I try hard not to do that anymore. But your right, I think I am getting attached. Especially to the infant, simply because I am trying to get pregnant, and she is filling that 'space' you know? :P

Yeah you can't let yourself get too involved like she has to have boundries set when she seems to be starting to overstep into your private time and things like that.