Hi there,
Unfortunately not everyone can be considerate of others or even comprehend what they're doing as wrong. It call comes down to whether or not you want someone external affecting the relationship between the both of you. It is hard to see these things, but he can't really control what she will post on her wall. The more you allow these things to cloud your mind, the quicker it will be to destroy your relationship.
If he does care about the relationship, mentioning that it is uncomfortable is more than enough for him to make his own decisions as to what to do moving forward. If he is serious he will raise the issue with this other girl. If you do trust him and believe in him, this should not be affecting you as much as it should. As long as you know that you are the most important to him, ignore the posts on facebook. Ask him to set his profile up to approve tagged posts before they show up on his wall and that way it's kind of a compromise and if he's understanding he will do at least that much to make you feel better.
Good luck.
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