USCIS laws varies for different cases for visa. Since you are a US citizen, I am not sure with what visa she can come, probably dependent or she can directly apply for green card. In either case, it should not take 1 year to process it.
If you don't marry, she will have to come on a visitor visa and would need a sponsor - meaning, a person in USA who is willing to bring her to USA for a short time, has enough in bank to support her and sponsor her medical insurance. That person would most likely should be you or her sister in USA. This visa may take months to process, yes, ton of paperwork, and may get rejected even.
Best to check with a lawyer.
On another note, with all due respect to you, if I am a 42 year old man, and a woman almost half my age tells me she loves me without even seeing me, then I would probably not trust her love. But I don't see any negative intentions on her part except for - probably looking for a better life in USA.
And if you love her and think it's worth sharing your life with her, then I don't see any harm in this marriage.
Good luck!
