VIRUS ATTACK! picked up repeatedly by avast resident protector... virus attack keeps coming! WHAT NOW?

my girlfriends daughter has been using myspace quite a bit and now has had 4 virus attacks in 3 wks? i put avast and malwarebytes on the laptop, the avast resident protection has saved this computer! avast resident protection has worked better than any AV that ive ever seen. but ive run into problems, 2hr ago we had another virus attack, the resident protecton displayed threats like trojan horse downloaders etc... the attacks seem too come like every 2 minutes... resident shield picked trojan after trojan attack and left me the option of removing threat too the vault? i repeatedly clicked the tab sending recognized viruses too the vault over and over? i then ran the malwarebytes antimalware quick scan... 8 minutes later the scan showed ZERO infections... SHOULD I HAVE RUN A THOROUGH SCAN OVER A QUCK SCAN? after running malwarebytes, i ran AVAST anti virus and its at 80% so far in the scan of the drivers.... will a scan of the drivers be sufficient? or should i run the scans of the folders, removeable media etc? also, avast runs very very SLOW! im wondering if this is a hinderance when you are attacked w/a virus? or if i should be ok with avast and it being slow because its efficient? avast flat out kicks ***! i know if i had avg or some other mcaffee i would be shut down right now.. but heres the question, the malwarebytes scan showed zero infections, but then after closing malwarebytes and starting avast av the avast resident protection picked up a trojan horse downloader etc.... so im confused! malwarebytes is usually kick *** man and this virus or worm is reappearing.... im hoping when this avast antivirus scan is complete that it has wiped out the infections.... any opinions from all of you technically minded folks??? THANKS IN ADVANCE!