If we assume your character is an average 140lb female athlete, then a normal strength would be something like.
- Bench-press: 40kg
- Squat: 60kg
- Deadlift: 72.5kg
These values are well above general population female averages, but since she cares enough to be a crime fighter, I will assume she is not on the couch potato side of things.
A standard, non-armor penetrating anti-personnel round is typically rated for about 12-18" of pentation against ballistic gel. Depending on gun and ammo type you could see a LOT more pentation than this, but I will use 18" as a basic starting point since assault riffles are generally designed around higher penetrations. So, lets call this 32x strength. This would result in:
- Bench-press: 1280kg
- Squat: 1920kg
- Deadlift: 2330kg
This is just strong enough to lift most cars.
The average assault riffle hits with about 1000 foot-pounds of force. An average nerf dart hits with 0.16 foot-pounds of force. This means we can assume you are at about 6250x strength.
- Bench-press: 250,000kg
- Squat: 375,000kg
- Deadlift: 453,125kg
We can pretty much stop measuring strength here for most practical purposes. By the time you get anywhere near this strong, adding more strength has absolutely no additional affect in most situations. Her feet will always sink into whatever ground she is standing on long before she can lift anything near this heavy, and the weight of her own body and lack of surface area means she will never achieve enough friction or counterweight to make any meaningful use of her full strength. She may in theory be strong enough to punch through that steel vault door, but all it will achieve is throwing herself backwards
... at least this was my original hypothesis, so I decided to try to calculate out the maximum size, maximum toughness obstacle your hero may ever need to overcome.
The hero will be best be able to exert her strength when trying to pull something apart or crush it between her hands, because this gets around her limited inertia issue. So, let's say a bad guy considers this, and decides to attack her with a killer robot armored with Boron Composite Fiber. BCF is not necessarily the the best material for stopping a bullet, but when it comes to tensile and compressive forces, it is some amazing stuff. It has a tensile strength of about 4GPa, and a Compression Strength topping out at somewhere around 6GPa, this stuff is REALLY hard to ripe or crush.
Our normal female athlete can butterfly curl about 30kg which is probably about her maximum crushing power. If we assume she is using the full surface area of her palms to crush this thing, she needs to exert her force over about 128cm^2 (54 per hand). Since GPa is measures by the M^2 and lift weights are measured against gravity, this means we can estimate she can crush pretty much any man made object with about 260,000x human strength (aka:~41 times as strong as scenario #2)... so turns out there is a use for greater than Scenario #2 strength after all, even though it is rather niche.
So, can catching a bullet with eyelashes girl do it?
unfortunately, this is a really hard question to answer since I can't find how much force it takes to bend an eyelashes, but... it may not matter. We do not know how much your hero catches the bullet by when she blinks it out of the air; so, you can easily say at this point she is at least 41x as strong as needed to nerf gun bullets off her skin, and that no material on Earth can actually restrain her.