Can the Cleric use her ability to prevent the loss of life from lifetap? and if so does the player still receive that life?

1) Yes, the Cleric can prevent the loss of life, since there isn't any special notation on the Life Tap card that says it is unpreventable.

2) Yes. Even if the life is prevented, the 2 effects from the Life Tap spell are separate from one another, and the caster would still gain a life. To prevent the caster from receiving a life would require Counterspell or a spell along those lines, but the Cleric ability doesn't affect the spell itself, just prevents the loss of life for themselves.

Yep totally agree with sanityismyvanity.

Tyvm