This enemy is the Alien variant of St. Pigge the 2nd. 100% strength magnification, Elizabeth has 60,000 health and deals 250 damage per hit. She also creates a Level 3 Shockwave with each hit. She has a range of 170, with area attack.
Elizabeth has high health (even more with the 700% boost) but relatively low damage and range. However, she has 100% chance for a Lv. 3 Shockwave, meaning that any meatshields are pretty much worthless: To beat her, use only strong, high-health troops, such as Mythical Titan Cat.
Anything that freezes Aliens and is decently bulky such as Surfer Cat, who can rush in without getting knocked back, can immobilize Elizabeth the LVIth, allowing other units to attack her without trouble (e.g. Valkyrie Cat).
Alternative Strategy (QUITE DIFFICULT)
If you have a high health base (80,000+), just spam Paris Cat (lvl>20). At first upgrade the Worker Cat and send 1 Paris to kill the peons. When Elizabeth comes out start spamming Paris and it's done. Elizabeth will hit your base but you will still win.
Scion of the cyber-pigpen, Liz almost ended her line after choking on a mushroom. She's still blue to this day. Uses powerful wave attacks.