How early are you actually breaking the lease? Is the lease end date August 1 or later? Or are you tenant at will?
I would still pay the July rent, and ask for the specific date you should expect to see your security deposit. There are laws about this that vary by state. I would also let them know that you want an itemized receipt for anything that your security deposit goes toward. I generally do this after I receive my security deposit and say: okay, I got all but $250 back. What did you spend $250 dollars on? And, by the way, they shouldn't take money out o your security deposit for cleaning or painting….cleaning, because they have to do it anyway, whether you leave a mess or not, so that isn't your problem, and most leases provide for normal wear and tear on walls and carpet, which usually means they need to paint and have the carpets cleaned.
If, for any reason, she does anything to your credit, you can call the credit bureau and dispute it. If it is an owner/landlord, in my experience they generally don't do much credit reporting, if it is a property management company, they usually do report.
Anyway, hope that helps a little bit. In the long run, you have already bought a house, which will probably help your credit more than this landlord can hurt it...