Can I keep unlimited data on verizon?

Can I keep unlimited data on verizon?
My iphone recently got wet and broke. I have unlimited data on my line of the family share plan. My mother currently has a "dumb phone" and is eligible for an upgrade. Is it possible for her to upgrade to the new phone (galaxy s4) and have that phone be transferred to my line so I can keep my unlimited data and then her just go back to her phone? Also, if this is possible, do I have to activate it on her line first or can I just transfer it to my line before the activation? My cousin says I don't have to activate it on her line first, but i've read other forums that said you did.

Ok so basically the thing is Verizon is phasing out unlimited data to new customers as well as existing customers upgrading to newer phones. Partly because of the new 4g LTE technology, they're trying to keep servers in a need basis. If you want to upgrade your line to a new phone for the 2-yr contract subsidized price, which is usually usually $200, you will lose your unlimited data plan. The only way to keep your unlimited data plan is to buy the phone for full price which is really expensive- $650 for the 16gb iphone 5 i believe.