I'd say just be honest.
Let your mom know that Your dream is to get into the NFL but that your looking into the military as a backup plan.
Then as you get more information about your primary plan and requirements/ conditions of your secondary plan you just need to keep your mom up to date. If your able to tell her gradually it may help her to accept it.
A sudden change is often much more stressful on a person than a gradual one.
I also agree with what the others are saying.
Don't forget to pray about it too, if you ask in sincerity the lord will give you an answer (though as i've learned from experiences not usually the answer you expect/want)
I didn't realize you wrote about this problem over a month ago, Has there been any progress?
