The secret to the fabled "blanket bomb" is to not try too hard. If she feels the gut tense she'll get paranoid and even touching the covers near her head will alert her to trouble. A casual touch of the covers may be enough to bring suspicion and foil even the best planned attack. Relax until you're sure it will be effortless. Distract her with a kiss and a cuddle while keeping a close eye on the best way to get the blanket over her face. Its easier if you can get the blanket fully over her head because the chances of escape are drastically reduced. Allow for enough time to ensure proper saturation before you let go of the blanket. Be very careful as counter attacks might be immediate and ruthless.