Vanessa, glad you found the link useful.
If she is already scared of doing No 2s, then it is really important that you do all you can to make sure every time she does go is as comfortable as possible. If she is v distressed and upset, you must try and be as calm and reassuring as possible. The trick is to make sure she goes without making a great big issue of doing a poo; easier said than done, I know.
Lactulose is a sugar (hence sweet and children tend to like it) which we do not absorb. So what you put in, has to come out . On its way through our system it absorbs water, making motions softer and easier to pass. As it is not absorbed, you can increase the dose every 2-3 days until the desired effect kicks in. What age is your DD? I have just reread the thread, but cannot see her age, however 10mls 2x/day is a middling dose and could probably be increased if need be.
Senna comes from a plant and is a so called "stimulant" laxative, ie it makes the bowel move. This is useful in getting things going, however not v good for longterm treatment as over many weeks or months the bowel could become ever more sluggish.
Movicol works in a different manner again, essentially by attracting water to the inside of the bowel much like Lactulose via a different mechanism. The paediatric version can be given up to 8 (!) sachets/day (depending on age/wt of child) sipped over the course of the day in 1 litre of orange juice, and, in my experience will get any child going , however can be quite explosive!!
All of the above can cause a bit of bloating, "windyness" and cramp, particularly at the start of treatment, and differnt things work and agree for different people. It is often a matter of trying things out, I am afraid. Once you hit on what works for you and your daughter, stick with it. Do not stop all treatment too soon. You can always reduce the amounts you are giving in the first instance and see how you get on.
Needless to say, make a big fuss of her, when she does go, praise her is she is brave when it is a bit sore - and keep going with lots of fibre and fluid in her diet.
Hope it improves soon. It is miserable, but will get better.