Your support and encouragement are crucial to her. Your wife needs to rest during the day, when the baby rests. Many moms use this time to get work done, but this can lead to exhaustion. Your wife and baby can nap together and both wake up refreshed. If your wife takes good care of herself, she will find mothering becomes much easier and less tiring.
Exhaustion can be a sign of depression.
Postpartum depression is more common than most people realize and is not limited to the days or weeks following the birth. If you feel your wife is depressed, it would be wise for her to be evaluated by her Health Care Provider. If you do decide it is the right time to wean your baby to a bottle, it is important to go slowly. Weaning is easiest on both mom and baby when it is done gradually. You can help your wife by offering a bottle when she isn't in the house.