I think your vet is being appropriately cautious wanting an all day observation and having an IV ready to go if she needs it. While its expensive I think that your vet is planning to do everything possible to ensure your pup makes it through vaccination safely. Benadryl is a pretreatment of choice but being ready to administer more with no fooling around time might make a big difference to your puppy.
I do think checking titers to decide what vaccines she may need would be a good idea.
You can read about titers and what they do and don't tell you here
http://www.caberfeidh.com/Titers.htm
and more here
http://www.canine-epilepsy-guardian-angels.com/titer_test.htm
http://www.doglogic.com/vaccinearts.htm
You might also want to keep your pup away from infection potentials and then vaccinate once she is over 16 weeks. You do a series because immunity from mom wears off at different times in different pups. Discuss that timing with your vet.
I would do minimal vaccinations with this pup to only the deadly diseases and only one at a time as needed. But discuss this in depth with your vet before making any decisions.
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