Is it possible to break the lease due to negligence by landlord?

If it is expressly stated in the lease, then yes.

Generally,a lease can be broken only when there has been a "substantial breach" of its provisions by the other party. You should consult a real estate attorney about the specific provisions of your lease and the details of the breach.

My first inclination is that a broken window isn't necessarily negligence on the part of the landlord in any event. If a broken window that went unrepaired by the landlord eventually caused a break in or something, you may have a negligence claim at issue, but otherwise I don't necessarily see it. Further, though, a tort, such as negligence, isn't typically grounds to break an otherwise valid lease. What the broken window may indicate, however, is the failure of the landlord to provide a habitable residence. Even then, though, the remedy at law wouldn't necessarily be getting out of the lease itself. What the window issue does provide, however, is leverage to negotiate an agreement between your daughter and the landlord that amends the terms of the lease. Landlords are often reticent to do that, of course, and there's no guarantees that they'd agree, but it's an avenue worth pursuing if you're left with no other options. If she's having difficulty, however, she should consider contacting an attorney in her area to assist her.

No, but she should advise the landlord in writing, give him a deadline to fix or she will fix and pay and then deduct from rent.

Not really. You can have the window repaired and deduct it from the rent. However, it would be a good defense for breaching the lease agreement.