This site has instructions for beaded bobby pins using beads and wire you wrap around the bobby pin -- hopefully you could do the same on a hair clip.
http://www.girlythingsbows.com/beaded_bobby_pins.html
If she is drinking constantly she needs to be checked for diabetes. Has she had a blood sugar test done? High and low blood sugars could account for some of the mood swings.
My dd HAD terrible mood swings as well from about 1 year to 4 years old. I can't exactly pin point what caused it, but she has some minor sensory issues as well (tags on clothes bother her, she has to wear a t-shirt under a peassant top I appliqued for her, the fabric on her Halloween costume bothered her, etc.). So she has something going on, but alot of her behaviour boils down to attention. We tried everything with her and I think we finally figured it out so that her drastic mood swings and hateful behaviour are now minified. The best way for us to handle her her bad moods are to give her what we call "alone time." We do this instead of a time out. We usually give her two options. One is to sit in the office and watch the aquarium ( we have a huge salt water aquarioum so fish watching is relaxing) the other is to go to her room and close the door and sit on her bed and read/look at books. Those have worked best for us. We can't put her in a regular time out b/c she won't stay and she will scream and get more and more worked up. She says hateful things and she will pinch, bite, kick, etc.
Our dd is extremely articulate and smart, but in the case of your dd she may have some issues as well with not being able to express herself clearly. Hopefully the speech therapy can help with some of that. And at a younger age alone time for your dd may be best accomplished by you sitting with her and cuddling and just taking a break (our dd wouldn't always let us do that though).
Now that our dd is older we can take some more extreme action. Like when she told me she hated me and didn't want me to be her mother anymore I took the weekend off (dh was home to take care of her). And when she locked herself into her bedroom and wouldn't open the door I took the door off for a week. Idle threats don't work with this child until after something with impact has happened.
When my daughter is sweet she's a doll and soooo loveable. But she can easily misbehave and have foul moods as well. Either age is improving things or our learning how best to handle her is. She really thrives on attention and compliments though and I always remember from my psychology class that if a child isn't praised or rewarded for positive behaviour they will perform negative behaviour to get attention b/c all they want is attention.
So in a nutshell, give loads of praise and positive attention. It may not solve any problems depending on your dd's issues, but it surely won't hurt. Also, mandate that your ped investigate the excessive thirst -- it IS abnormal. And also, you know your own child best, so if you feel a psychological evaluation is necessary push for one as well. It may help give you some answers or set your mind at ease. You're the mother -- you're with your child constantly and you obviously know things aren't quite right. Don't settle for "no" with the pediatrician.



