I read through the post and my response to your last thread still stands. Just be friendly with her.
I think you should meet other women and forget about this girl but I know you won't so here is the advice I'll give you that might help you.
FYI, I never ask women out. I meet women in non-romantic contexts. If I have something cool I want to see or do, I invite a girl if she wants to join me. That way I can get to know her better in an environment with less pressure and expectations, doing something I was going to do anyway so if she flakes or isn't that fun of a person, no matter.
@TheNinja has the right idea.
So here's what I would do. I make small talk, ask her about her day, talk about weekend plans, etc. If she asks what I'm doing I'd be like, "I'm going to go surfing/hiking/volunteer at a dog shelter/dancing/etc."
"That sounds fun!"
"Oh, do you want join?"
Say it really casual. Throw it away with no pressure implied. Don't say it like you're trying to interrogate information out of her so you can ask her out. That's why it's important to do shit that is interesting in your regular life. I'm not going to invite a girl I don't know to join me if all I'm doing is watching netflix in my underwear this weekend.
How you say it is really important. And how you say it is often a reflection of how other things in your life are going.
If you say something with enough suave, you can say almost anything. But at this point, you do not so act with more caution.
Definitely do NOT comment on her legs though. Imagine if you were talking to a random fit guy about his workout routine. Are you going to open with, "Hey man I've been checking out your legs. Do you squat?" He's doing to think you're creeping on him lol. If you must talk about her body and ask her about her workout, maybe just joke about how strong she looks.
I do think you should set your sights on other women though. Get rid of your scarcity mindset. Realize that physical beauty isn't everything. She might be a really shitty person inside. Maybe she tortures kittens for fun.