what we know:
love interests are sentai colored
Flora - heroine = pink
Mikhail - prince = blue
Vladforen - dragon king (hidden route) = black
N (can't remember) - Demonic horse house guy - Red
??? other colors, probably green, yellow, silver, maybe purple.
One of those is probably Alexi's estranged childhood friend.
since the prince is the blue one, there is no Alexi (or Ekaterina) route.
With Rina steeling the prince and dragon routes from the heroine (and possibly the heroine route), that means the 'blue' route is vacant, so Alexi could be romanced by Flora in that case (if Rina doesn't steal that open spot in the romanceable by heroine).
Vald is the final boss on all routes but his own (so his route may be the 'true route').
on the prince's route, if Flora messes up, Vlad destroys the kingdom.
Rina has not only stolen the ques to get heroine affection from the prince, she also managed to get affection from the prince and stumble onto the hidden route for the dragon king (and seems to have high affection with him as well).
Not sure if Flora is on the BFF route with the villainess, or if she's trying to be a love interest for Rina as well (I'm thinking Alexi for Flora, but will have to see).
The poor prince has been upgraded from avoid at all costs to good friend, but has also been completely friend zoned. As Rina only sees him as a kid, I don't' see any hope for this relationship (regardless of if he's author approved or not). The age issue will be a huge hurdle (more than possible death flags). Someone in their 30's will even see collage students as kids, so there is no romantic interest in them. By the time the prince is old enough for Rina to consider him a romantic partner, she will have already been married off. Same goes for almost all the other love interests.
Vlad has the Rina can talk to him about her past life and doesn't have to hide anything going for him, on top of being an actual adult. Plus he is a dragon and she would be able to stay by her brother's side, as the duchy is in the dragon's territory. Has the added bonus that Rina is attracted to him (even if she's fighting it due to the trauma of her past life and fear of the unknown). Has being a dragon as a negative though, as Alexi does not think well of that. Does have the advantage currently over the other love rivals for Rina, as he is the only one she knows is interested in her (proposing does that).
As for Rina, she has the trauma of her ex-stalkers and is scared of the unknown of falling in love. She is actively sabotaging herself when it comes to any romantic feelings and is hiding behind her stanning of Alexi to power through it. Sometimes I wonder if her denseness is a defense mechanism and not just her not noticing people being interested in her (which is believable. it is much harder to notice when someone is interested if they are being subtle to ones self then noticing when it is others where you can see from a somewhat objective standpoint).
She is a bit more dense then I am, but as I have trouble telling when someone is interested in me or flirting with me (I can sometimes tell, but it is not easy. most of the time its my family who's like, that guys was into you, why didn't you talk to him type thing), I see her behavior as how she is, plus a product of her trauma.
Rina pushing her relationship management onto her brother is definitely a defense mechanism, plus he is the deciding factor due to the society she is now in.
I also wonder if it would be possible to get a 'good ending' without Rina ending up with Vladforen. I can also see a bad ending if anything happens to Rina, as Vlad will act if she gets killed (and a new wasteland will appear with the epicenter being whoever was responsible). It is a good thing he is not following her to the capitol, as who knows how he would react to anyone trying to bully or do worse to her.
The real question is will Vladforen respect and accept Rina ending up with anyone but himself. He seems reasonable, but he is a dragon. I cannot see him accepting Rina being forced into any relation ship (nor would Alexi, Flora and Mikhail), but not sure what his reaction would be if she actually fell in love with someone that is not him.
Personally I see Flora X Alexi and Ekaterina X Valdforen. I just can't see anyone Rina's physical age being a partner for her due to her mental age.