They were. During their time with the Women’s Wrestling Federation their manager arranged for them to have their natural abilities augmented by the Power Broker. Mel received enchancements to her vocal implants and also got other cybernetic implants. She wasn’t as strong or superhumanly enchanced as, say, Titania or Letha but she was no slouch.
OK, that’s what that wiki says, but that doesn’t make it canon. I think if you look at those issues of The Thing you’ll see that Mimi is never directly shown receiving the enhancements and she never displays any signs of mega-strength; in fact Mimi only appears once, in a brief cameo in Thing #33, in the entire UCWF storyline.
Now, the lack of direct evidence doesn’t prove or disprove that Melissa got super-strength; you can interpret it either way. But the bottom line is that she hasn’t demonstrated any super-strength in the last 25 years. (As I recall, Melissa’s first post-UCWF appearance was Avengers #271, where she fights the Wasp and the Black Knight; you’d think if she had super-strength it would be using it there, but she doesn’t.) So the simplest explanation is that she never obtained super-strength, or that it wore off shortly after she gained it.
For what it’s worth, I remember Kurt Busiek being asked about this on Usenet back in the ’90s, and his opinion was that Songbird had no super-strength and just didn’t undergo the Power Broker’s treatments. Of course, his opinion isn’t canon either (seeing as he never wrote it into the comic) but seeing as Songbird has never gone around bench-pressing cars, it has the advantage of being consistent with what we see on-panel.
Happiness that was alto brief
The only thing that would make me happier is if they remember that along with the rest of the Grapplers Melissa had also received cybernetic implants enchancing her strength and other physical attributes. That would make my day.
Are you talking about their involvement in the Unlimited Class Wrestling Federation storyline from The Thing? Because I don’t think the super-strength those wrestlers gained were the result of cybernetic implants. There’s also no direct evidence that Melissa underwent the treatment that gave (for example) Demolition Dunphy and Battleaxe their super-powers.
Unless you’re referring to something else entirely, in which case I’m totally stumped.