Learn Russian: Она тратит время.

Yes, тратить generally means to spend money or time. However, when used with время without mentioning a productive purpose, it often carries a negative vibe, implying the time is being spent uselessly. To be very clear about wasting, Russians often add зря (in vain) to make тратить время зря.

What case is время in, and why didn't its ending change?

It is in the accusative case because it is the direct object receiving the action of the verb. The word время is a special neuter noun that ends in -мя. Because it is an inanimate neuter noun, its accusative form looks exactly the same as its nominative (dictionary) form, so the ending does not change here.

How does the verb тратить conjugate, and why does it end in -ит here?

The verb тратить belongs to the second conjugation group because it ends in -ить. For the она (she) form, you drop the -ить and add -ит, making it тратит. Be careful with the 'I' form, which has a consonant mutation: я трачу (I spend).