No, not the US. Only UK. She can go to some European countries but you would need a Shengen visa for that country. She can goto Turkey for a holiday, no visa required for Thai passport.
If you trust her it's the same as going into business with someone in your own country! Don't get your question really! Depends on you, her, business, everything. There is no single answer.
If you trust her, do it. If you Don't trust her and asking strangers on fb for advise,....don't do it