No, the time between the collision of the Andromeda galaxy and the Milky Way cannot be considered "half" because neither galaxy is moving faster than the speed of light.
According to our current understanding of physics, objects with mass cannot travel faster than the speed of light in a vacuum. The Andromeda galaxy and the Milky Way are both bound by the laws of physics and are not exceptions to this principle. They are, however, moving towards each other due to the force of gravity between them.
The collision between the Andromeda and Milky Way galaxies is expected to occur in about 4.5 billion years, based on current scientific estimates. This is a long time in human terms but relatively short on a cosmic scale. The collision will be a slow process, taking millions of years to complete, as the galaxies interact gravitationally and merge over time.
It's important to note that while the galaxies are moving towards each other, the expansion of the universe is also taking place, causing the space between them to increase. However, the gravitational attraction between the galaxies overcomes this expansion, eventually leading to their collision.