Question: Although I usually practise mindfulness of the name of Amitābha Buddha (i.e. Āmítuófó: 阿弥陀佛), as I once felt very desperate, I then pleaded to both Āmítuófó and Guānshìyīn Bodhisattva (观世音菩萨) for help. Is this alright?
Answer: It is best not to switch, or add another enlightened subject of mindfulness — because it might express lack of faith and focus in one of them. It is better to stick the one you have most faith in directly.
Do bear in mind that the Bodhisattva mentioned is the leading disciple of the Buddha mentioned. Guānshìyīn Bodhisattva is usually seen as the compassionate aspect of Āmítuófó, which means Āmítuófó already has her perfect compassion. Being connected, there is no need to change focus. The power of prayers comes from sincere focus.