I am assuming that this potential date is at least somewhat open to discussion. The first thing I would do is hunt for those washtowel articles that contradict other washtowels. You will have plenty to pick from, and that could include issues about oral sex, organ transplants, and 1975. Getting close-dated articles around 1975 is a good idea--if you can find an article urging people to sell out with a late 1974 or early 1975 date, and a "blame the victim" article around 1976 or 1977, all the better.
Beyond that, you will have to use your Bible. Whether you believe in it or not, remember the witlesses claim to go by the whole Bible and even use the scripture about all scripture is inspired to back that up. You could start with Ephesians 2:8 and 9, telling us that salvation is by grace and not works. Luke 2:10-14 is another good place: That discusses the first Christmas party in heaven, among perfect angels. 1Thess 4:11 is another prime scripture--mention that it tells people to mind their own businesses. At which point, bring up that the "friends" are urged to be loyal to the Washtowel Slaveholdery and rat out people for doing things that are really none of their business. The goal here is not to get her into a new religion but to show her that the Washtowel, while claiming to use the whole Bible, does not.
Prepare for interference from the hounders. Even if she is open, the hounders are going to do all they can to bust this up. Their prime tools include "shepherding" calls to blow you off, talks about worldly associates, and setting her up with so many assignments in field circus (which could include calls) designed to prevent her from seeing you. They may even approach you, telling you to leave her alone unless you are willing to join the cancer (in which case, you would have to study with another man, wait an indefinite period of time before courting, and watch her get taken out from under your feet). The ultimate goal is to get her to disassociate or to become totally inactive, at which point the hounders will not be able to do anything.
Now, if she is totally unreceptive, you would be fighting a losing battle. From the opening, that doesn't look like the case here.