Contrary to popular belief, you can ask her out and still remain good friends if she rejects you. This is simply due to the fact that what destroys the friendship isn't asking her out, but rather making a fool of yourself when she rejects you. This worst-case scenario would unfold like so:

You wait for too long and catch way too many feelings. When you ask her out, you're totally lovesick. You arrange a beautifully romantic date in a secluded spot, with rose bushes and everything, perhaps you extend a trembling hand and offer a wad of love poems you wrote for her, and then you're overcome by your feelings and you become a bumbling fool, and you move in for the kiss...

In the movies, she kisses you back with violins and everything. In real life, maybe she does if she's interested. However, if she's not interested and "doesn't see you like that" then...

• The "beautifully romantic date in a secluded spot" is a tricky situation to get out of.
• Your investment puts high pressure on her. You created a situation where rejection is difficult, awkward and costly for her.
• If you drove her there, then you will have to endure all the drive back in total awkward mode.
• If you start crying (because you're too lovesick, remember) and she consoles you, she will consume the entire energy of the friendship in doing so, after which it will no longer exist.

We haven't hit rock bottom yet. This would be when, the next day, you get drunk, and then a wonderful idea hits you: you're going to ask her out again! Maybe it'll work this time. You start with a long apology, then follow her in the street as she walks away, and then you insist, and then... oh yes...

Your excessive feelings increase the likelihood that you will say the Stuff That Should Never Be Said, like "But I was so nice to you!!! Why do you reject me!!!" which is the totally nuclear option. There is so much wrong in this sentence, she will treat you like radioactive waste for the rest of your life.

Then, of course, the following week you learn that she's dating Chad from the football team, and you conclude that Chicks Dig Jerks and that women are evil for not wanting to date you, such a... a... such a NICE GUY! In other words, you cast upon yourself the cringy curse of the Nice Guy. You die alone, bitter, and a virgin, but at least the fedora looks good.

Another option is:

• Rid yourself of the fear of rejection, as it is what will cause you to create the worst-case scenario above.
• Do not fear awkwardness.
• What you will say when you attempt to initiate the relationship (ie, ask her out) does not determine if she is attracted to you. Either she is already attracted to you because of looks, personality, and past behavior, or she is not. Asking her out doesn't need some magic formula or anything. Either there is attraction or there isn't. Asking her out badly can ruin it, but it can't create attraction.
• Considering your current friendship, pick a low-pressure setting: you're both swiping through your favorite meat market app and showing each other matches and giggling.
• At the appropriate point, just mention, "hey, why don't we date each other instead of doing this?"
• She says yes: you score.
• She stays silent and gives you the googly-eyed stare: wait five seconds and laugh it off. If you're lucky, she was actually interested and now asks you out.
• She says no: you laugh it off and go back to browsing. No drama. Not fearing rejection means you don't get butthurt or whiny, and you do not exhibit Nice Guy symptoms…

Note: Edited for brevity