Most likely she placed a bid higher than all the bids you just placed so the system did an auto bid for her until the bidding reaches her high bid. Ex: my bid is 2306 but the current bid is 347. Every time someone places a bid lower than my 2306 the system will outbid them by just a few credits until someone places a bid higher than 2306. Hope that helps explain what's happening.
There's really nothing I can do. If you strongly feel that someone hacked, than you need to file a report with Listia. But I don't think that is the case here as I explained on your other comment. Good luck. ☺