Would you take money from your child?

I have a little sister who is 5 and she’s the best thing to ever happen to me and I want to give her everything she wants so I setup a savings account for her and also whenever I see her (we don’t live together) I always give her money to put in a little money pig for her. However I went her house and gave her a coin to put in and she said she can’t because her pig is gone so I didnt understand what she ment so I asked my mum where her pig was and she stopped for a bit to think and then said I dropped it and it broke so I had to throw it away and when I asked where the money was she said she’d laid it all up somewhere safe so I thought nothing of it. However she needed a new school bag and I had no money because i hadn’t been paid from Work yet so I thought I’d take it from her savings account since it was money to spend on her which is what it’s for but when I got there apparently all the money had been withdrawn already and they said a woman with dark hair took it which is my mum!! So I questioned her on it and she argued with me saying she had bills to pay and had no money to pay them and they needed food and said the money does go on my sister for a place to live and food on the table btw my mum doesn’t work and does hardly have any money but they always have alcohol in the house so it’s annoying they have money to buy alcohol but not to pay there own bills. I think there was better ways than to steal it and Im positive she used the money from the pig n broke it on purpose.Does anyone think she’s right that shes entitled to the money to pay her bills or would u say this is wrong?