Is this thinking and grieving over a deceased husband considered angering God, knowing that the wife tries to resist her sorrow by praying, reading the Quran, and performing tasbeeh?

There is no justification for worries about shortcomings if you have not been negligent. Rather, your duty is to be patient with Allah’s decree and submit to His command. Sadness does not contradict patience as long as it does not lead you to say or do anything that contravenes the Sharia. Know that all of Allah’s decree is mercy and wisdom, and that the outcome of patience is a great good. For whoever is afflicted by a calamity and says: "Indeed, we belong to Allah, and indeed to Him we will return. O Allah, reward me in my calamity and replace it with something better than it," Allah will do that for him.