I know most of the time it's Wilma Slaghoople, but I seen some other episodes
when she referred as Wilma Pebble???

From a Flintstones FAQ:

In the episode "The Entertainer" (P-44), Wilma's old friend Greta Gravel remembers her as "Wilma Pebble" -- which we can only assume was her maiden name. Again, in "Dial S for Suspicion" (P-74), one of Wilma's old boyfriends calls her "Wilma Pebble." Yet in later episodes such as "Bachelor Daze" (P-112) flashing back to where she and Betty were working as cigarette girls and they first meet Fred and Barney, Wilma's last name is said to be Slaghoople -- a perfect example of Flintstones quirkiness.

Flintstones FAQ (http://www.topthat.net/webrock/trivia2.htm)

all shows from the 60's and 70's had inconsistencies!!