i don't think you should have to deal with his friend hanging all over him. she should respect the fact that you two are in a committed relationship (heck, going to be married soon!) and backoff. it doesn't seem like she's very happy that her "boytoy" is being taken away from her by another woman, but that's her problem.
i see that you've talked to your fiance and he has "forgiven you for being jealous". i think you have every right to feel the way you do. there are two sides to this coin, one being her flirtations and the other being him. has he stopped her from hanging all over him? does he acknowledge that she flirts? has he even considered what this is doing to you emotionally? if you aren't comfortable having him around her, he should definitely take that into consideration and look at the situation. you two are to be married. you don't want this girl butting into your relationship a couple years down the line when you have children and things are more complicated.
communicate to him your thoughts about how this is affecting you and also your worries about money. you two are starting a life together and the only way to get through is to communicate, communicate, communicate.
i think you are quite a calm person in this situation. personally, i probably would have already told her off
but thats not exactly the best way to deal with things. good luck, and congrats on the wedding