my little sister steals my phone?

[soup]

hi, i'm 19 and my sister is 14. every time i pull out my phone to text my boyfriend, and i mean every time, she tries to snatch my phone out of my hand or read what i'm writing. then when she can't get it, she'll whine nonstop saying, "tell me what you're saying to each other! i wanna know! if you don't show me that means you don't love me!" and i say, "no, cuz you're going to tease me and tell everyone what it says." and she says, "no i promise i wont!" every once in a while she manages to steal my phone and she'll look through all my texts, and sure enough next time she's near my parents she'll say, "guess what jake (my boyfriend) said to anna (me)???" and she'll run around telling everyone and a lot of times it's personal stuff, and what can i say to her to make her understand that the texts are for me, and i don't want to show her, but it doesn't mean i don't love her?