Am I being taken advantage of by my workmate?

I work with this girl who is younger than me.. I have worked there longer but I am trying to decide whether she is taken advantage of me.. Of she cant actually do it because she is actually busy..I always offer to help out.. Even when I dont have to..and now I feel people arnt doing things because they will think “nah ill leave it,, I know she’ll end up doing it” (meaning me).. But I dont always… And if I dont my boss will start to think im slacking.. Or not bothering as much now.

If we get asked to do something.. She always say.. No can you do it because I have to do this…or… If you start it ill come and help you

. 1 time I didnt do something for her. She said that her arms hurted to much… I said… No.. You do it..u’ll be fine.. And she got in a stress as if it was my fault..but if someone more senior asked her she would be all nice and just do it while they are there.

1 time I had a pen clipped to my sleeve.. She took it with out even asking and walked off.. I know it sounds stupid but if it was someone more senoir.. She wudnt dream of doing it with out even asking. But because it was me..she did..

Even my boss has said im too soft…

Im not sure if shes trying to have controll or take advantage or what.. Some 1 please tell me whats going on,, and how I can be more assertive.. I want to become where no 1 will even think about trying it with me.. I want more respect..

But now …if were is at work doing nothing..theres 4 of us.. And I usually say something like.. Right… Things need to be done.. Im gona do this and you lot can do that… Is that the right way to go?