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It is pretty normal for pups to do this. There isn't much you can do except to keep her looking at you and your hand. The easiest way is to start training your pup using hot dog slivers. The hot dog slivers gets the oil on your hand and the pup will be very interested in your hand and not you ankles. I know it is impossible to constantly have hot dog slivers but you can have practice session which will help the pup learn to walk at your side and not behind or in front of you. When she does get your ankles, you can spray a diluted citronella spray at her which may help. They don't like the smell at all.
The other thing you can do which is very helpful until she stops the ankle biting is to walk with an exaggerated gait. You need to bring your heels up about 12 inches in the back. When you walk like this, if the dog attempts to get your ankles, they run the risk of getting a heel in their chest or under their chin. It only takes once or twice before they avoid sneeking up behind you. They still might try to come at the side or front. For the front nips, keeping the feet moving forward usually will push them out of the way and they get tired of that. You have to be careful not to kick her but they still get the message.
You can also carry a chew toy that might help keep her distracted from your feet. You can attach one to a stick so you can wave it in front of her when she is nipping your heels.
The following site is helpful in helping owners train their dog. Be sure and click on the link to the page on obedience at the bottom. and links on subsequent pages leading to detailed instructions. At this age, they learn quick so it is the perfect age to start this.
Training works best if you train at least 30 minutes a day (two 15 minute sessions) and for this age start with only 5 minute sessions. I would start making your dog work via the Nothing in life is free program (NILF). It is outlined below.
I hope this information is helpful to you. If you would like any additional information or have more questions please don’t hesitate to press the reply to expert or continue conversation button so I can address any issues you still have . If you do find this helpful, please take this opportunity to rate my answer positively so I am compensated for my time.