After Jesus's talk with Martha (as well as Martha proclaiming that she believes Jesus is the Christ), Martha called Mary and told Mary that Jesus was coming. Mary then went and was followed by many Jewish mourners.
Eventually, Mary reached Jesus and fell down to His feet. The falling down to feet is commonly used as a sign of worship and submission, and Mary likely did that because she too saw Jesus as Christ. Afterward, Mary told Jesus that if Jesus was there, Lazarus would not have died.
Mary's comment is very similar to Martha's comment. In fact, the question on God and suffering (also known as the "problem of evil" question) is one of the biggest and most common questions in Christian history and even today. Even people from Bible times had this question. The good news is that God understands the frustration people have with the question because there are instances of Biblical people asking such questions.
Dealing with the "problem of evil" question is a large ordeal, but John 11 does have a few pointers. First off, we know that God is not happy when suffering happens. Later on, we'll see that Jesus wept. Additionally, as mentioned early, we know that God (and Jesus) had a plan to use the bad scenario to reveal Himself to the disciples (and also Mary, Martha, Lazarus, and even the Jewish mourners). In fact, God has often used instances of suffering and brought out good for others. His actions are similar to how some people make art out of wasted goods.
For additional resources, there are online resources from sites like Character of God and folks like Paul Ellis that discuss the question and provide even more insight.