My sister has no idea I spy on her when she masturbates in the garden of our house

In the Thursday evenings, my sister has the habit of going to the back part of our garden and after laying a blanket on it, she gets ready with oil to start masturbating. I have known this for two weeks and have taken the dare to watch her while she does it. It’s hard for me to accept that my older sister’s body is becoming attractive to me, but how can I explain these desires to go to her and penetrate her and show her that I can be a big man who gives her pleasure. For me, she is everything and I don’t want anyone to penetrate her. With a lot of passion, she touches her vagina and begins to moan erotically, her vagina gets wetter and wetter as she feels her fingers touching her clitoris and all her vaginal lips, I hope she never catches me masturbating while watching her.