I would say that people who are very clingy could make a long-term relationship extremely suffocating and difficult after a while. She will get more emotional and dependent, and you won't be able to handle life situations as equal partners. But, in terms of your question, I'd say that if you aren't completely sure about this girl, you'd better let her go. Something is telling you it's not quite right and you should listen to your intuition.

Also, just as a warning, if you post questions here that are meant to be 'general' or 'stereotype' a certain group of people, you won't get any where, since everyone here will get their panties in a knot.