Aweee, you have a great heart for helping people and you cannot ever be faulted for it! But, you also need to know when to stop so you are not stepped over.
I'm glad it's working for her, and you need to tell her that and point her in the right direction where she can now take over for herself to buy her own supplies and learn more about it.
Maybe direct her to these forums and give her the name to a couple vendors in your area for her to visit.
All of ^^ This ^^
The next time, just tell them where you got the equipment (have a business card on hand) point them to the liquid place you purchase from. Do not offer to do it for them. Once you start, it is hard to get off that train.