I am going to put my 2 cents in and disagree here. Sorry. I'm not an expert cake maker but I still practise making cakes and give them to my mum. I am currently on a diet so I'm off eating cake for the minute. (Yes its extremely hard, I LOVE anything sweet.) Because she is my mum I obviously do not charge her. I'm not tight fisted but I wouldn't make cakes to get me experience for friends unless it was their birthday. However, I would bake them for friends if they offered me cost of ingredients and gas. I wouldn't want money for my time. That's just me. I know you said you get hair done for cake making and that's cool! If the cake is for her! I completely understand what you're saying about finding that one person who can do your hair just how you like it.
Look at it from this point of view, she clearly isn't giving these cakes to her friends, when I say friends, I mean friends not clients! Her friends would know she hasn't baked them. If she is giving them to friends, I bet she is saying, 'hey, I know a woman who bakes cake, I can get discount, let me know what it is you want and I place an order with her!' She then probably takes her friends money, which is rightfully yours! On the other hand, would you take a cake from someone and not offer them anything for it? I wouldn't, it would make me feel bad for not offering at least ingredient money.
If it was me, I would say that you're going into business so you will pay for your hair to be done from now on and if her 'friends' want cakes making that she passes your details to them as you would like to get a list of customers.
I'm not saying that's what you should do, that is just personally what I would do as I feel she is mugging you off!
If she had any respect for you, she would comply with that. Anyway, that's just my opinion. Hope you manage to do what's right for you, and good luck if you decide to set a business up.