The gardasil shot only protects against 9 of the most common strains of genital HPV. There are dozens.
Your ex's HPV test being negative just means she doesn't have active HPV at the time of the test. It doesn't mean she doesn't have it.
The activities you are doing are low risk, though.
Condoms offer significant protection against HPV, but not total protection. There is a chance, but not a high one.