A blister is not typically a sign of spider bite; however, it could be. Like most other wounds attributed to spiders, unless you catch the spider in the act of biting and observe the swelling, redness, or whatever, you can't be sure it's a spider bite at all.
This worried parent describes serious signs of infection, including "redness the size of a chip ahoy cookie." It seems our concerned parent is sure of the infection part of this enigma, even though his or her submission doesn't mention seeing a doctor.
Blisters of the skin can occur from burns, friction (like those you get from your shoes), or infection. Spider bites may lead to blisters, but these other causes are much more common.
Any unexplained blisters warrant at least a call to the family doctor. In some cases, blisters can be a sign of serious infection.
Any opinions expressed here are for educational purposes only and are not intended for diagnosis.