How do I serve a "pay or quit" notice to a sublet tenant that is not paying rent in a timely manner? Is there a specific form? How do I send it so that her signature is on the receipt? The May rent was paid on June 8 only after an appearance from the management company and pressure from the other tenant that is living there. She's only paid $600 out of the $901 that is was due for May and June. She has been late ever since March and every time we get notice from the management company and ask her about it, she says she's going to pay next week. Tried calling the parents with no response. Tenant herself does not answer her phone or email.

I am Texas and the property is in State College PA

Here's a link to a PDF file for notice to pay or quit:
http://www.wimer.net/landlord/free/3daypay.pdf
It's for California, but I think you'd be able to cross that out and write Pennsylvania, instead.

Odds are that she won't pay, which means you'll have to file for eviction.