How old are you? "single" in a bio either means she's in middle school or probably not good dating material. Mature women (and men for that matter) are self aware enough to realize advertising their singleness isn't very classy.
Anyway, here's my suggestion. Go up to her next time you see her at the parkrun, have a conversation with her. I'll give you some pointers, since I assume you're a younger person who doesn't know how to do this:
When she's not talking with anyone else, go up to her and start with "Hey, great run!" Then, ask her a question to get a conversation started. "What was your result today?" "Do you do these regularly?" Follow up with something relating to what she says. Don't keep asking her questions like its an interview, just have a casual back and forth flow from responding to the other person. At some point, say, "by the way, my name is [your name here]". She should say something along the lines of "oh, hi, my name is [name]"--if she doesn't follow up with this, it's OK ask "and what is your name?" Sometimes the girl can be just as nervous and not be thinking about proper conversation etiquette. Do your best to give off an aura of self-assuredness--not overly confident, but no sign of nervousness. It will help to put both of you at ease in your conversation.
Eventually, when your conversation is done, you can just say "well, [girls name], would you like to grab some coffee with me right now, or perhaps some other time?" If she says yes, you're in. If not, tough luck, but credit for trying.