Hello, I am a solicitor with 20 years experience. I will try to help you with his.
If the damp is caused by a defect to the structure or exterior of the property then that is actionable disrepair that the landlord has a duty to repair. Compensation may be payable for a breach of this obligation. If representations were made that the damp would be fixed and the contract was entered into on the strength of those representations then that might be a cause for legal complaint as well, even if the damp is not caused by a defect to the structure or exterior.
If the pleurisy was caused by the damp then the seriousness of the situation is greatly increased. It will be important to obtain evidence about the extent of the damp to support any claim that this caused the ill health. Inspection by a surveyor or Environmental Health officer may well be necessary.
There are some practica points here though. How long has your daughter lived there? Has she made complaints in writing about he damp? Does she wantto stay tehre? When does the tenancy end?