I am not familiar with any nasal version of the feline leukemia vaccine, but you should be aware that there has been quite a bit of controversy related to the FeLV vaccine and the development of sarcomas.
Because of that possible correlation and because I have seen quite a few cats that react poorly to the vaccine (who feel very crummy for several days), I have opted not to vaccinate my own indoor cats. I test any cat before bringing it into my home (beware stray kittens!). But that is my own individual choice.
As to your cat staying with friends, make sure that those cats have been tested negative for the virus (“But they’ve never been sick” does not count.) If they were positive before being vaccinated, they’ll still be positive. Unless your own cat is particularly sociable, it will probably need to be kept separate from her cats anyway to avoid fights and resultant injuries.
I would not get the vaccine because of this visit. Talk to your vet and make an educated decision about whether or not to vaccinate your cat for this disease. And keep in mind that as an initial exposure, your cat will need a booster in 2–3 weeks. It may take several weeks for your cat to develop an immune response, so giving the shot a day before going to visit will not incur protection. (I always laugh at boarding kennels that give a “kennel cough” vaccine on arrival, as if it creates instantaneous protection.)
Vaccination protocols and recommendations can be found here