Family joining Visa Expiry

Can anyone tell if, my spouse visa will expire in-case she is away from the country for more than 6 months, even if the resident card and visa both are valid.

No. Irrespective of whether your wife resides in Oman or not, the validity of her dependent visa and the resident card is 2 years from the date of issue, unless you cancel it anytime in between.

there till now no problem she can inter oman
may may be you check new rule coming must need 6 month 1 time entry to oman