I am not the primary line on our account but I have used two upgrades un the last 4 months with no problems.
The primary line is linked to the plan any secondary line will not renew the primary plan.
If you and your GF are on the same plan just upgrade the secondary line one day and then go to myverizon.com and transfer your upgrade to the secondary line and upgrade it again. But after upgrading transfer the second device to your line.
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