Hello new daddy!
Welcome! I'm sure you will got lots of responses and ALL kinds of different opinions on this subject. We all have done what works best for our families and maybe some of our advice will work for you.
I've never heard of Sleepy Planet but just looked up the website. For me, I think its kind of silly to have to pay someone to tell you how to get your child to sleep. Parents have been putting their children to sleep for years without the assistance of sleep counselors, and without the added stress of paying for one. Hopefully some of the advice you receive here will help you...and for FREE! :o)
Children have all different stages of development that can wreak havoc on their sleep patterns. If she begins to sleep thru the night again, there will come another stage in her life where she will wake again at night. I have two boys, 5 and 3....and both still go thru certain phases where they either sleep all night, or sometimes come into my room for various reasons at night. They do go back to their own beds, because frankly, I have a hard time sleeping when they are in bed with me and I've learned that it is much better for them to return to their own beds because they will have a much happier Mama when I get a full nights rest. Sleep deprivation is an ugly, ugly thing. :o)
What has worked for me is a little method that I'm sure a lot of parents have used. One question though...is she teething? This could be keeping her up at night; she could also be going thru a growth spurt and her little body is restless. Maybe if you can narrow down what might be bothering her, it might be easier to get her back to sleep (Of course, if it were THAT easy, we would all have everything figured out!). A little pain medication (for teething..Orajel, Tylenol, there are also homeopathic teething tablets that dissolve on the tongue)
With my boys, if I knew they weren't sick or hurting...I would give them a little milk (formula) and if they started crying when I left the room, I would let them cry for about 3 minutes, then go back in their room, pat them on the back or bum and tell them "Its ok, Mama is here, its time to go to sleep". They would continue to cry, but each time I went in the room, I would increase the time between visits. I would not pick them up or turn on any lights, I would talk in a whisper.
I would start with 3 minute increments, then move it to 5 min, then 10 min, then 20 and so on. The main thing is, CONSISTENCY!!!!! YOU HAVE TO BE CONSISTENT!!! It will take a few nights for her to get the hang of it, but she will. You just have to be consistent. (of course, this is all my opinion and what worked for me.....)
Also, do you have a bedtime routine? Since my boys umbilical cords fell off, I started giving them nightly baths (didn't always use soap, warm water works just as well) we would feed them, read a story and put them down to bed. Of course, they didn't fall asleep quickly every night. Its also a good idea to put your child to bed when she is sleepy, but not all the way asleep, that way she can learn to fall asleep on her own.
If she has been sleeping soundly until now, I figure there may be something going on with her. I'm assuming teeth....that causes lots of sleep disruption and she's at the age to start working on getting some teeth in. Sometimes they get them right away, sometimes they can work on getting a tooth for a couple months. If she is going thru a growth spurt, she may need more food as well. Since my boys were little, I've always had a fan in their room. (facing outside the door if its wintertime and inside their room for summer heat) I think the 'white noise' helped them sleep. We have lived in apartments so it also helped with keeping OUR noises more camoflauged (if that makes sense).
I hope some of this helps. There are many different cultures and ideas out there, we just need to find what works best for us. You may have to try a few different ones before you find what works best. Just remember to BE CONSISTANT!!!!!!!
Take care and good luck!
S.