It's pretty normal for little kids (especially girls) to rub their privates on their toys because they discover if feels good, just like little boys who play with themselves as well.... however there does come a point when it isn't in the normal range, when it becomes obsessive and the child stops finding other ways to play or self soothe. Undressing is also fairly normal. My boys always would take off their clothes at night... i just slid their underwear back on and put a heavier blanket on them in case they got too cold. However, if she is acting provocatively or like she has seen or experienced something she should not know about, or acting out sexual scenarios, then you should definitely speak to her pediatrician about this b/c that is a major red flag... kids get molested all the time by their friends/family, so it isn't impossible that it hasn't happened.
We talked to my boys when they were 3 about being touched inappropriately. Teaching them young is really the best way to go. What kind of touching was okay, to say no, to not keep secrets for any adult or child who tries to touch them, that anything in the bikini area is NOT okay to be touched unless it is only for cleaning by a trusted caregiver, and if it is uncomfortable of goes on for too long, then to fight it and say stop and report it.... Only family and the Dr can see us naked, and only when bathing/changing clothes/getting a physical. We even tell our children to report if mom/dad/Dr is touching inappropriately, we want them to know we will listen to them and protect them.
Dr. Sears is an expert in this field and he has an article called "Genital play, what's normal and what's not". It has some great advice for you to consider here:
http://www.askdrsears.com/topics/child-rearing-and-develo...
and:
http://www.askdrsears.com/topics/child-rearing-and-develo...