Visitors tourist visa

Yes...she can do what they call  "Airport to Airport" where she flies to oman and return back to UAE with a different visa on the same day. All she has to do is book a flight to oman and back on the same day ( they are often cheap flights for that on Flydubai). Make sure she already have the new visa with her upon traveling.

You could get her 90 days visa from many tourism outlets here in Dubai without a hassle, just google UAE visa. If you do not find let me know, i could recommend you one.

Hello,

A tourist visa is valid for 30 days with a 9 day grace period to exit the UAE.  Earlier this year it changed to a multiple entry tourist visa so if you leave and re-enter within the 30 days you DO NOT get a new visa you simply have the remainder of the 30 days of your original visa plus the 9 day grace period. If you leave before 30 days you will receive a new visa if you then re-enter after your original 30 days has expired. The date of entry/stamping counts as day one. There is no need to exit the UAE for 24 hours to renew a tourist visa.

If you leave after the 30 days, in the grace period of 31-39, then you can immediately re-enter and receive a new 30 day tourist visa.  A lot of people here do this and it is known as a visa/border run.

As the poster above says your wife can fly to Oman but as you are in Abu Dhabi I would recommend this company who can take her by road;-
facebook.com/abudhabivisarun/

Is she goes in the grace period, 31-39 days, then the total cost will be 385DH.  300DH for driver and pick-up, 35DH exit fee from UAE and 50DH fee for Oman visa. Takes about 5 hours for the whole trip. If she has already gone beyond the grace period there will also be the added cost of overstay fines.

Hope this is helpful.
ExPattyCake