In my experience, this will resolve itself quite soon, people don't like to be single so if you don't land with one quickly, they'll get snatched up.
You apparently know your female friend, why did she 'leave'? Do you two have a bumpy history? Is she on the rebound?
If she is serious and loves you, then I'd say don't take chances that the unknown one will turn out. Grasp love where you can find it, don't gamble.
There's plenty of time to gamble when you've got no other choice. =)
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(14.01.b) cogito ergo sum confusus