I feel confident in saying that she is capable of handling any situation with thoughtfulness and maturity. Three to five paragraphs is enough and certainly no more than one page. This will give her a chance to ask someone else who might be able to write a stronger letter.
During the years of our acquaintance, I have worked with Katherine in many capacities. If you're not asked for a reference letteryou might consider offering one anyway.
Pick someone who you think will speak positively about you. Mary is a bright young woman, and I am sure that she will excel at whatever job she undertakes. This can be a great way to make your job application stand out if you don't have a very strong employment background, maybe because you haven't worked in a while or because you're new to the job market.
English, Mathematics, Science and History work samples can be found as PDF documents below the year level achievement standards in each learning area.
Be sure to emphasize how much you appreciate them taking the time to write you a reference.