You should file Married Filing Jointly, and in fact this is highly encouraged. That way you will get $24K exemption for this year from IRS i.e. more tax refund. For immigration purposes, it will only strengthen your case with USCIS.

You will have to file form W7 to get an ITIN from IRS for your wife. The US embassy in Kathmandu also provides services to notarize your wife's passport specifically for the purpose of applying W7. Check out their web page at
https://np.usembassy.gov/u-s-citizen-services/local-resources-of-u-s-citizens/notaries-public/

Let me know if you wanna go that route. I can post more if you need more details.