You need something portable, so I would suggest, at her age, the Safeseat30. Its an infant seat, so it would work for other area's, it rear faces to 30lbs, and most kids can easily use this seat to age 2. Its a bucket type seat that has abase, but can be used without the base.
At her age she NEEDS to remain rear facing, so a portable seat like the ridesafe Vest would NOT work for her, she's way too young. If you want somthin to carry her around in, a higher harness infant seat like the SafeSeat 30 or a Chicco Keyfit 30 is your only option.
Once she outgrows that, it would be acceptible to use a vest type car seat for her.