I stole $40 from my mom and I've been so scared to tell her

When I was like 4 I had about $40 and I lent it to my friend. So, I went to my mom and said "Mom, my friend owes me $40 and I haven't gotten it back yet". She then told me I was a 4 year old and that I should know that you don't get it back. Then she asked me why I lent him all of it and I was so ashamed because I had no answer to that. She then told me to go talk to him and explain to him that I want my money back. So, I did. I got my money back and I kept it a secret. Now I'm 17 and my mom wants me to get a job so she can teach me a lesson. I told her I already have a job. She then asked me how much I was making and I told her I wasn't sure. She then told me I needed to let her know every time I get paid so she can teach me how to save. I feel so ashamed that I can't even tell her the truth because I'm afraid of getting in trouble.