We've been together for 2 months. It's not a lot of time, but we live in the same shared house, so we spend tons of time together. Also, we don't call each other bf/gf.

The relationship is convenient for me, for some practical reasons, and for her as well. At this point of my life, I am VERY overloaded with many things, so dumping her would be impractical, as she helps me with everything. And I do feel like we like each other.

Having said that. I feel like crap when she does that when we are together. I don't mind whatever she does when she's not with me.

Besides simply telling her not to do it, is there anything I can do to make her stop it?

Yeah. Stop doing that and get over it. Honestly. You gotta grow out of that boy phase. It's so unattractive for a man to be jealous. If you're not a man, you're jealous. Let her be her. If you're afraid of losing her, you'll lose her. Period.

If she did it for a short while, it may have just been a test to see how secure you are.
If it carries on, you need to up your game to show that you are a high status guy.
It may just be that she is with you for convenience too, but will trade up as soon as someone better comes along that she can grasp on too.

Bring in other options for yourself, jealousy (from her) works great

Set clear boundaries. Communicate your discomfort with her checking out other guys. If the relationship is more than convenience, make sure you both respect each other. Ask her straight up what's going on and decide if it's worth continuing.