I was diagnosed with severe OCD last September. Since that date, I have been receiving wonderful support from specialists at Altrincham Priory. In order to assist your daughter, you need to have a thorough understanding of various elements of OCD.

As your daughter has been diagnosed with this terrible illness, I know that she will have some, if not all of the following traits:-

She will not be able to tolerate uncertainty. She will think in extremes, black and white with little grey, she will have an over importance of thoughts and an inflated sense of responsibility. By that I mean, she will tend to think that she should prevent harm from occuring on all occasions, that thinking bad things is as bad doing bad things.
Let her know that everyone, wehether they have OCD or not has inappropriate thoughts. The difference between people like her and I and others who do not suffer is that we attach meaning to our thoughts.
This meaning has 4 consequences. First of all, anxiety. Secondly, the need for reassurance. Thirdly a compulsion and finally attentional bias.
Anxiety will not significantly harm your daughter and with a planned hierarchy of fears, she should be able to engage in ERP. This is exposure and relapse prevention. Overtime, she will notice that the anxirty decreases. She must stop seeking reassurance. You can play a part here by not accommodating the OCD. The final two are the most difficult. She must stop her compulsions. This is
achieved by ‘detached mindfulness.’ I can explain further if you need me to, but basically she must neither reject or engage in the thought. Finally, whatever her obsession is will lead to an attentional bias. For example, if it is contanimation, she will notice ‘germs’ a lot more than others. She must acknowledge this, not reject it or engage in it.
I have provided you info’ here that took me twelve 2 hour sessions to get to grips with, It is not easy.
I hope that this assists.
Lumpy