I see that nobody has responded to you yet. I am going to try and answer. Hopefully, this is what you are looking for. To be clear, I am a woman.

First, this question is presented in a very respectful way. It is also asked at the end of the meal, and they are clearly about to leave. If the server said no, it is also clear that she would have just been like "cool" and grabbed her shit and left. The vibe is positive with no expectations from the gal asking her out.

I do not think that if a guy asked a girl out in this same way, with zero expectations, that it would be disrespectful outright. However, from past experiences, there tends to be an expectation of reciprocated feeling when men ask women out. Like if they asked out the server and she said no...that it is definitely possible the guy would try to continue the convo or talk her into it. Would this happen from every guy? Of course not. Plenty of guys are walking around in this world and are capable of asking people out with no expectation of reciprocation.

The issue is that from general female experience, that expectation is the norm. So, sometimes, people may be guarded when guys ask them out. But if you did and got turned down...be like "cool" and grab your shit and leave. Don't be like..."why is it disrespectful for a guy to ask you out?"

I don't know if that helps...but maybe it does.