you say "hey its been cool doing this project with you, later do you want to hang out and get lunch or something" and then exchange contacts. thats it that is actually it dont worry about anything else people tell you.

the vague intentions of "going out to lunch" makes it so its not so obvious its a "date" so neither of you would be as intimidated. from there you just talk to her like you would anyone else and see if you click

i only pursue after asking variations of that line if i got an enthusiastic yes. for the "ummm i mean sure but im not in town often" or variations thereof dont bother its probably going to be awkward