I connected my laptop to the home network and got a popup of ip-conflict issue; i neglected it and opened Tor browser.. and my sister using her laptop ordered some stuff on amazon using chrome..now both of our devices had same ip address..Is this a problem,,did her amazon order request went through tor relay..Im really worried..
IP Address conflict errors mean that the router is sending any traffic to and from your computer to both computers with the same IP Address. This means that if your sister opens up Firefox and visits Google the router would send back the data from Google to both computers. Luckily most modern operating systems are aware of this misconfiguration problem and would simply drop the traffic that's not intended for them. Unless the other computer is acting maliciously (e.g. its infected or if your sister is secretly an evil hacker after you) there's little to worry about. When you have time fix the misconfiguration on your router and all is well.
As for the Tor Browser Bundle, your connection between you and the relays is encrypted, your sister's computer does not have your set of encryption keys and therefore can't make sense of the data and has no choice but to ignore it. Your sister's computer not having your set of encryption keys would be unable to route traffic within your Tor circuits.
Next up as for Amazon - connections to Amazon.com are always routed over HTTPS so the connection between your sister's computer and Amazon.com is encrypted. Even if you can watch all traffic between your sister and Amazon.com, without the keys you can't make sense of the data. The same applies to the Tor network, a malicious exit doesn't have the ability to make sense of the data. Although in your case your sister's Amazon order likely was not routed through Tor.
And lastly the majority of Tor exits are operated by well meaning individuals or organizations. The odds of you connecting to a bad Tor Exit are quite low compared to the odds of you connecting to a good Tor Exit. This is not to say you shouldn't take reasonable precautions against bad exits - it's just something to keep in mind.
Hope this helps :)