megansleia Do the female sim and the sim she flirted with still have any red showing in the romance bar? If there is, you need to get the relationship to 0 or negative. You also need to get rid of any romantic relationship like gf, bf, of romantic partner if there are any between the female and sim she flirted with (or anybody else other than the one you want her to have a romantic relationship with.
You can empty the bar by having the female invite the other sim over use the ask to be friends' option on the Relationships submenu. Then ask the visitor to leave before either sim can autonomously do a romantic social.
You can also use the cheat to set the romance level to zero between the 2 sims. Here is the cheat: You'll need to change SimA and SimB to the names of the involved sims. "modifyrelationship SimA SimB 0 LTR_Romance_main". It will drain their romance bar completely.
Once you clear any romantic relationship she has with other sims, then it's a matter of time before she stops getting the thought bubbles. However, that does not mean that all of them will stop. You might get one every so often since the sim is still a friend. It seems to work about like RL does in that the game will give you one of a random sim your sim has met at some point in the sim's life and shows up in the relationship panel. The only way to get rid of them about a particular sim is for both the friendship and romance bars to reach zero and the sim drops out of the relationship panel.
Hope this helps.