Visitor's Visa to Canada for El Salvadoran?

My friend has been refused twice for a temporary resident visa to Canada by the Emby in Guatemala. No reason really - they base it on statistics and she had all the paperwork needed. She then applied for the USA visa and got it right away. So, my question is, if she wanted to cross the border to visit me from the US, is it the same process? Can she cross at Niagara for 48 hrs? Can she get a tourist visa from within the US if she has all needed paperwork with her? Will the computers have her 2 refusals in Guatemala on record? We are getting ever closer to meeting but do not know what to do next. Thanks.