i guess no one will be able to answer your question as it depends on many factors. in general i would say no need to worry. there people with way more entries every year without a problem.
both is possible. there is always no guarantee if u do a border run that they will let u in. but rarely happens and mostly to people who did this way more pften than u did
they always asked for usd. the visa fee is announced on all official websites in usd. nowhere its stated in baht. ofc they accept thb but the amount isnt equivalent to 40 usd.
and it was like this already ten years ago when i came to laos the first time.
dont complain if u havent done proper research before u go
its important that she can either prove to have enough money or u will have to prove that u can pay for everything and that she had reason return to thailand (working contract (is the best), family, other duties). they are mainly afraid that no one can pay for her and that she wont go back.. (strange thinking)