You can teach your puppy the "settle on your mat" cue. Here is a great video on how to teach your puppy to settle on a mat:
http://www.youtube.com/watch?v=jQ0Rii_5ckE. Once your puppy could settle on her mat, increase the criteria slowly by standing and walking around while she settles on her mat. This will let her learn to do other things, in this case is settle on her mat and not chasing and chewing your pants while you walk. Once she achieved this, drag a long tug toy beside you as you walk. Play tug with her in as she heels beside you. The tug toy is use to direct her attention from your pants to the tug toy so that she will learn to walk beside you but not chew at your pants. Once she can tug at the toy and walk beside you over a short distance (for example: 15 steps), reduce the amount of steps when she tug. For example, let her tug the toy beside you as you walk 5 steps and let her walk beside you without tugging at the tug toy or chewing your pants for the next 3 steps before letting her tug again for the next 5 steps and let her walk beside you without tugging at the tug toy or chewing your pants for the last 2 steps and give her lots of praise and a jackpot of treats at the end for her wonderful behavior. In this way, you can gradually increase the amount of steps without her tugging at the tug toy or chewing on your pants and decrease the amount of steps which she tugs at the tug toy while walking beside you until she can walk beside you for the whole distance without tugging at the tug toy or chewing at your pants. Patient is the key to success and most importantly, set your dog up for success. Here is another video that teaches you how to teach your puppy not to chew on your fingers:
http://www.youtube.com/watch?v=c77--cCHPyU. I prefer the above methods that I have stated to the spray bottle method or the time-out method which you put her in dark spare room that you use as I tried the spray bottle method to stop my dog from barking when she is a puppy. It spoils my bond and relationship with her and she is so scared of the spray bottle that she run away whenever she saw one. It makes my heart ache when I saw that. As her owner, she should be happy when she sees me no matter what I do but instead she is so scared of me and always cautious of me and the spray bottle. I should also help her overcome with her fears as her owner instead of adding fears to her life. Some dogs will be scared of the spray bottle at first but after a few times, they may get used to it or even enjoy it and think that it is a game as they have fun "biting" the water that comes out of the spray bottle. When this happens to your puppy, the spray bottle method is no longer useful, instead, it might reinforce the behavior and cause the problem to become worse. To me, the spray bottle is a control to the problem, not a solution to the problem as if she chew your pants but you do not have a spray bottle around with you, you cannot control the problem. It is the same for the time out method. If she chews at your pants when you are walking her out in the park where there is no room for you to put her in, you cannot control the problem. Putting her in a dark room might also lead her to being fearful of the dark which will results in more problems in the long run. As you carry her and put her in the dark room, she might associate having carried with a negative result which is going to the dark room and no more attention. She will not let you carry her if this continues and it will become another greater problem for you. Hope these methods and suggestions help you and your puppy. Have a great day with your puppy!