Daughters usually drive parents mad - fixing the TV will not necessarily help.
You have:
1) An Aerial
2) A Cable from the aerial to the wall socket in daughter's room
3) A cable from the the wall socket to the TV
4) A TV
No 1 may be bad but it would be most unusual
No 4 has been shown to be OK
That leaves 2 & 3.
Eliminate 3 by using another cable as a test
Examine the socket in daughter's room for poor connection
Send someone up on roof to examine connection between aerial and cable (do this last of all).
Good luck...
Peccavi
March 2009