I have read the entire thread, and i can see both sides of this coin.
Yes you were lied to, you are bound to be concerned over a repeat of this, and at the same time annoyed.
I think the up front cleaning is reasonable, but as others have said the extra £pcm and 28 days maybe a little much and i can see why you've (planned to) request that, i just think maybe you should reconsider.
I think you could be in a worse situation as others have said. Yes she has lied and this is by no means any justification for lying, but.. she has probably been a little desperate in finding somewhere that will house her. If she has come from a break up as someone suggested, then this will have added to an awful situation for her. She has dogs that dog owners will understand are as loved as family members, so she didn't know what else she could do. She may have lied because she was desperate, not because she was an impulsive liar who was trying to get one over on you. If this is nipped in the bud then chances are you'll have a good tenant. The fact that she has rung you to apologize and paid a 6 month up front deposit surely sends signals of what kind of person she is?
As you say though, you need to be sure of that rather than just instinct, i'm just suggesting another angle to view from that is all.