My sister is a liar and a thief

Hello, i am 19 years old and have 3 sisters. the youngest whom is 14 years of age appears to have a serious lying and stealing problem. Most recently tonight for example a pair of my expensive shoes that i wear almost daily suddenly disappeared.  When questioned on the same day she said she had not seen them so i believed her and carried on searching, this search became so extreme we had all family members looking after weeks and weeks of asking daily if she had seen the shoes and her lying she turned up this evening with the shoes crying saying she had hidden them in the office and that she didn't know why she had done it i was so angry when she did this but was not at all surprised because my instinct was that i knew all along it was her. this is not the first time this has happened. when i leave the house she raids not only my room but my other sisters rooms to find things that she wants then hides them in her wardrobe this has happened many times yet when the clothes are found she still lies about taken them and blames my parents on putting them there. its not just clothes she steals but money, nice expensive underwear and make up.  My mum has tried taking away her possesions, grounding her, shouting at her, threatening her that she will not tollerate thieves and liars, talking to her calmly and explaining what she is doing is wrong, i have even tried talking to her calmly and i thought it was working . nothing is working and this has been going on for a couple of years now and its starting to worry me that she is not growing out of this horrible phase. Please help !!  

[grungema3]

hi alex. I am an ordinary mum with 2 daughters and one sister. I am also a teacher so know a bit about teens. Lets look at the positive. Your sister is not taking the stuff and selling it for drugs. It happens, as you know. This started when she was 12, just when she was approaching adolescence. I'm sure you have all thought about the fact that she wants to be grown up like the rest of you but quicker?
As the baby, just maybe, only an assumption, she might have been a little  more spoiled? Maybe having more leeway than the older ones when they were her age? I know my younger daughter and my younger sister were allowed more grown up activities  earlier than I was or the elder daughter was.
Everyone is addressing this problem absolutely correctly. You sound like a lovely family.
Apart from putting locks on all your drawers and cupboards, totally impractical, I think if she was mine, the best way forward would be for Mum to give her a cuddle and  to say gently that this is not looking like a passing phase, and it may be more helpful for her to see a counsellor? The pertinent comment here is that she doesn't know why does it. If it carries on it may be wise for her find out her reasons with a professional. It's nothing to be ashamed of if she has to seek outside advice. Both my girls have and I'm a teacher and supposed to know all the answers! Good luck and hope that your lovely family will soon be free of your problemx