Ten year old sons 25 year old half sister?? HELP?

Q: My ten year olds half sister who is 25 yrs old talks to him via thier seperate myspace accounts. I told him no more and emailed her a note that said her myspace material and contents were inappropriate for her little brother. Now her family (my exhusbands) think I am picking on her...do you think I was right to tell her this was inappropriate..I do!!! The pics were of a drunk woman ped out on a sidewalk with a mini skirt on pulled up and panties showing her sprawled out widespread with see through panties and another cartoon pic of a mans and some lewd comment...I am furious she would subject him to this...also the definition of "bit%$h spelled out in an adult manner...Note she is a mom of two a boy aged 4 and a girl age 2 my ten year old sons nephew and niece I don't think she would like them seeing this crap at ten??...I am outraged and glad I spoke my peace. What would you do?? Sorry So Long...need support here one way or other...xxoo