Legally, she cannot kick you out. You can call police if she tries. She must use your states' processes for eviction.
As a practical matter, it appears you will need to find a new place soon--start looking and maybe you can find a new situation before you incur the costs of a defense against the eviction process.
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You need to find somewhere to live. The apartment is your girlfriend's and you have no rental agreement with the property's owner. Also, most residential apartment leases contain clauses prohibiting a sublease from a tenant to a 3d party, and so, you would probably not be able to argue that you had an agreement with your girlfriend.
Bottom line, this sounds like an unstable environment, especially for children. You should find a new place to live.
The foregoing does not establish an attorney client relationship with Attorney Stephen D. Gregg. The information given in Attorney Stephen D. Gregg's answer is not legal advice and is only given for educational purposes.