I'm not sure from your comments that she has actually said she is giving it every day....but you've assumed she is.
You say she said she was giving it regularly when child was ill, and that when you saw her again she was giving it. That is not the same as regularly giving it every day.
So think carefully, has she actually said she gives it every day and regularly across the day? Or is it that she's spoken about giving it, you've seen her giving it and assumed she does this EVERY day?
There's quite a difference here and it's worth thinking about what you actually know and don't know for sure.
Good friends talk to each other about tricky topics, even when it's hard. If you're worried you need to talk to your friend even if it doesn't go down that well. All you need to do is while chatting, say you just wondered how often she's giving the baby painkillers, as you'd noticed it the last couple of times you were with her. You can point out what the packaging says about how many days or doses can be given in a stretch without consulting the doctor and that giving more than that on a regular basis can be dangerous and ask if she was aware of that.....if she says it is very regular. Or you can ask if she's had medical advice to give it that regularly.
I would certainly speak to her first, especially if she has never categorically stated she gives painkillers every day to her child on an ongoing basis.
See how she responds.
Going straight to social services or some other organisation, especially if she has never actually said she gives them every day on an ongoing basis, but this is just your assumption based on the fact you've seen her give them several times, and she's mentioned one or two spells of ongoing use, would be jumping the gun and based on insufficient evidence.
Has she actually said she gives them every day on an ongoing basis?