All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
If this girl is in general religious, meaning that she observes her religious obligations, especially the prayer, and she avoids committing grave major sins, and you expect that the marital life will be stable between you and her, then we advise you to marry her. By doing so, you will be kind and dutiful to your parents who asked you to marry her, in addition to what you said about her that she is attached to you.
In any case, the economic status of this girl is not a religious reason to refuse marrying her. Moreover, if her childishness does not affect her religion, then there is no harm to forget about it, and if she is still young, then such a conduct from her could be a result of her young age.
On the other hand, if her faith is weak, like if she abandons the prayer for instance, or that she does not abide by the Hijab, or that you really fear that the marital life will not last between both of you, then we do not advise you to marry her, and your parents have no right to force you to marry a girl whom you do not like to marry. As regards the possibility of her committing suicide, if this really happens, you are not sinful as she will be the one who committed the sin.
Finally, if marrying her is not predestined, then you are obligated to totally cut the relationship with her as it is not permissible for a Muslim to have an affectionate relationship with a non-Mahram woman and what you experience in this regard is due to your disobedience, and you are both obligated to repent from what you did in the past. For more benefit on an illicit relationship, please refer to Fatwa 81356.
Allaah Knows best.