re: health issues, just get tested for peace of mind (odds are you're fine)
re: Girl, I think you struck upon a genuine girl who is into foreigners and wanted a guy who wasn't just chasing her for sex / throwing money at her. "Prostitute" is kind of a grey-area in SE Asia - she probably has other guys who send her money, as you say. Sometimes girls can feel like objects when that happens and they want to find a guy for something real, where it isn't all about sex-for-money - so when she came across you she had a chance to feel that way. Sounds like a fun adventure.
re: Girl, I think you struck upon a genuine girl who is into foreigners and wanted a guy who wasn't just chasing her for sex / throwing money at her. "Prostitute" is kind of a grey-area in SE Asia - she probably has other guys who send her money, as you say. Sometimes girls can feel like objects when that happens and they want to find a guy for something real, where it isn't all about sex-for-money - so when she came across you she had a chance to feel that way. Sounds like a fun adventure.