Answer
(Fatwa: 1148/959=D/1430)
It is better and afdhal that the wali (guardian) of mature girl is present in the meeting of Nikah or the Nikah is solemnized with his permission, but it is not necessary for the validity of Nikah. So, if a mature girl marries a boy of his match (kufu) with due process, the nikah will take effect whether the wali is present or not. Therefore, the aforesaid Nikah performed with match (kufu) is valid.
Allah (Subhana Wa Ta’ala) knows Best
Darul Ifta,
Darul Uloom Deoband