If in Pattaya, go to Bangkok Bank on 2d Road, near Soi 6. I was able to open an account there 2 years ago, on Visa Exempt stamp. Just needed to get a Certificate of Residence at Jomtien Immigration, based on TM 30 filed by hotel. Piece of cake. And they are always very helpful everytime I do business there.
They probably have arrangements for you to take a different van or bus on the Cambodian side of the border. You should call to get clarification from them
I had a rental car. Left it at secure parking lot on Thai side of border. Walked across border. Ignore guys saying they will get you a Cambodia visa. Just walk to the Cambodia visa office and get it yourself. On the Cambodia side, there are many private taxis who can take you to Siem Reap. Last note, there is an area with Casinos between Thailand and Cambodia, which is like a visa free zone. You have to walk past this area to get to the Cambodia visa offices.
Warning: Men in the US are crazy and obsessed with Asian women. The amount of attention, pickup attempts and offers an Asian female will receive in the US is overwhelming. So an Asian lady landing in the US, will suddenly feel like she is the most beautiful and desirable lady in the World. So it's not surprising that a beautiful 22 year old, is testing the field. She's feeling the same way we feel when we land in Thailand.