Not heroine. Hero, period. While it's rad that Ellen Ripley happens to be a woman, that doesn't at all impact her level of badarsery — though it does inform her character in ways that make her much more interesting than virtually any other cinematic hero. She's complicated, she feels real, and I have total confidence the Alien movies would not have become classics without her.
Image from Alien via screengrab
When we first meet Ripley, she's just an ordinary person with a job to do. She isn't in charge of the Nostromo, but she has a certain amount of authority as warrant officer, a job that she clearly takes pride in. When crew member Kane has his much-too-close encounter with a Facehugger, Ripley is the voice of reason, reminding everyone about the necessary quarantine period. When she's undermined, first by Dallas (who orders her to disobey the rules) and then by Ash (who pops open the door, since he has secret motivations of his own), she's pissed. But she's still a team player. She cares about Kane and while she doesn't forget the slight, she rolls past it in the interest of tackling the next crisis at hand.
That incident — which obviously ends up proving Ripley so completely right, because of course you should not let that guy with a damn alien clamped to his face onto the ship — moves the plot forward into horror movie territory, but it also illustrates the level of human (artificial and otherwise) crap Ripley has to put up with on a regular basis. Obviously fighting the alien is the flashier way of demonstrating one's heroism, and Ripley does that capably using a variety of tactics. But her employer and some of her co-workers are the other monsters in the Alien movies. Imagine going through all of the events of Alien, only to wake up decades later in Aliens, surrounded by a snooty, dismissive panel of corporate superiors who flat-out don't believe your story. Burke, Paul Reiser's sleazeball company-man character in the sequel, is arguably the biggest menace in a movie that still features a giant alien queen that oversees the annihilation of an entire space colony and the deaths of multiple Colonial Marines.
Somehow, Ripley is able to get through the movie without strangling Burke, even though his behaviour endangers not just the crew, but also potentially the entire human race if he's able to carry out his plan of bringing alien specimens back home. And Burke isn't the only idiot-with-power that Ripley has to contend with in Aliens. Lt Gorman puts the whole team at risk when he proves incapable of making quick decisions when things are crappy. Meanwhile, Ripley is capable and cool-headed in nearly every situation, to the point where she just takes charge when the Marines' initial investigation into the lost colony at LV-426 suddenly becomes a bloodbath. She knows when to follow the rules, but also when to break them, that sometimes you have to disobey an inexperienced leader, and most importantly, what's most important is getting all the survivors the hell away from a terrible situation.
Obviously, she is extremely brave, but she's also human. She gets scared. She has nightmares. In Aliens, she sparks with Hicks and feels a powerful maternal connection with Newt. She even loves Jonesy the cat. And her emotions are capable of evolving. When she first meets Bishop, she's suspicious of him because of her bad experience with the insidious Ash in the first film. But as things fall apart in Aliens, she can still recognise that Bishop is incredibly loyal and self-sacrificing.
A lot of Ripley's triumphs as a character are obviously due to Sigourney Weaver's intense and layered performance; even in Alien 3 and Alien: Resurrection (in which Ripley... isn't Ripley), she is the most magnetic thing in them. I saw Alien: Covenant last night, which I went into with very low expectations and ended up enjoying more than I thought I would — but its biggest problem may be that it has no Ripley. I don't mean her, specifically; I mean there's no remarkable central character for the audience to connect with, to care about. Nobody will walk out of Covenant remembering how awesome the hero was.
For all its attempts at delving into the Alien series' mythology, Covenant is really just a big, silly monster movie set in space. There are lots of movies that fit that description.
But there is only one Ripley.