I do not know of a simple tool for doing what you asked, but I offer the following alternative. I think this breaks down into two problems: converting an XML file to something more amenable to a graphing package (for example, a CSV file), and then instructing the graphing package to convert the data into a graph.
There are a variety of methods for extracting data from an XML file; your choice will depend on your personal preferences and your programming skills. For example, I believe nose is a python tool; you could use one of the Python XML parsers to extract the data and produce a CSV file. Depending on the XML file's format, and if it is convenient for you to use Unix command line tools, you may be able to extract the data using awk, grep, and sed.
If you Google for "convert csv to graph", you will find many tools for graphing your data.