labmate stealing ideas
If your ideas were fleshed out experimental plans that someone else took and used, that's not cool. You should complain.
If your ideas were a bunch of &quot;wouldn't it be great to study this topic&quot; thoughts, that's just not enough to stake a claim. If the PhD student is acknowledging that you're also in that area I wouldn't complain. You should ask her for help designing and executing an experimental plan. The best outcome is that she teaches you some new stuff and you both end up coauthoring something solid.