Ah--now we are getting somewhere.
It is much better to pick you University of choice by the faculty and subjectr researched than by the name alone. You will be spending 4-5 years in the laboratory, working at least 50-60 hours a week (unless it is a time of pressure, and then the workload goes up). So if you don't really love what you are doing, the name of the University will bring little comfort.
A few words of advice:
Apply to several Universities (5-10---and I am not kidding). Make sure that each of them have faculty and programs that interest you. It is not necessarily a given that you will get into the program at Hopkins--and you may find other programs and researchers that interest you more. Start with a PubMed search for papers that interest you and then look for the authors' affiliations.
Your visit to Penn State was a good idea. Now--see if you can repeat it at Hopkins.
First, get your application ducks in a row. Did you take the GREs yet? Be in touch with the secretary in charge of applications to see what you need to do beyond what is posted on the website.
Then, read every paper that Dr. Griffin has written in the last few years (at least the ones on her website). You should do this with a couple of other faculty members at Hopkins as well. For all you know, Dr. Griffin's lab may be full up--always have a plan B.
This way, you can be sure you understand what she is doing and why. Because your next step is to email her and tell her that you are applying to Hopkins and are interested in her laboratory. (She will ask you why.) Tell her the truth. Professors are always looking for students that are excited about their work, and like people who have done their homework. With luck, you can get an invitation from her to visit.
Keep in mind that she may not be able to respond--and if that happens, do not hold it against her. She may be traveling, or in the middle of a massive grant application, or something like that. According to the Dept. website, she is also the department chair so she is basically working two full-time jobs.
best of luck to you.