You can use "foot blisters" in that sentence, Budspok. In my experience, people usually say "blisters on her feet" to express the idea. "Mechanical irritation" sounds rather technical and unusual. In everyday conversation, it would be more common to hear something like "Her new boots are rubbing her feet and giving her blisters."
For your last sentence, I'd use this version: My new shoes have given me blisters. It's also possible to use "blister" as a transitive verb: Those new shoes blistered my feet.