OK thanks. If you can see a lot from the ground - she'll be able to judge herself.

she would NEVER go on any of these....Guardians sounds like a definite no.
Guardians is WAY tamer than Space, EE, or RnRC.
I would also like to add STRONGLY that the best approach is to let her decide what she wants to ride. If she is prone to suggestive fear, then probably the worst thing you can do is to tell her in advance that a ride will be SCARY.
The BEST way to overcome fear is to give her as much control as possible. If she is 18, then she is very much old enough to sit out a ride on her own. A really solid approach would be to give her choices in the moment. Then contact each other by phone if you split up. Maybe pick a place to meet up before you ride?
Second, if it has been a few years, I'm not sure how to say, but she has had time to change. The same attractions might bother her the same, or they might not. I have years of experience working with teens. One day, they just make up thier minds they ARE going to do something and then they do it, evne though they would not do it the day before. I've seen it many times. A really key thing is THEY have to decide to do it. Fear is often about lack of control. It can also be planted by others, especially parents.
If possible encourage her to see the queue and preshows with everyone, then just use the chicken exit if she is scared to actually ride. (usually just before you board the actual vehicle.) Even then, if she opts out, she can use that time to do a quick alternative. Like maybe visit gift shop. Guardians has a very cool gift shop.
I ESPECIALLY encourage her to go through the queue and preshows for Guardians! They are probably WDW's best ever!
I HATE the suggestion of watching videos. People scream when they go on rides, and that often makes rides seem scarier than they are.
A good way to give her control though is to talk to CM's. They can provide her non-biased ride facts. Just a few specific facts will help her feel control. The ride is X minutes long. The top speed is 30miles per hour. Another option is for her to count during the most intense part of the ride. Knowing the 'intense' part is only X seconds long= more control. It gives her a tool for combatting the unknown, especially on re-rides. Closing her eyes is another option. (I know that one is obvious, but it can make a big difference).
Rise is mostly pretty tame. The drop is very small and very quick. Honestly, the ride is just so-so IMO. We have taken to skipping it when we go to HS, and saving ourselves the hassle of waiting for it/breakdowns. I agree Minnie/Mickey Train is a good pre-option.
Smugglers is an enclosed space, but not otherwise scary. If Star Tours makes her queasy, or enclosed spaces bother her than it could bother her, but otherwise it is just a game, and not a super one at that.
As others have said, she will be able to see Slinky before she rides. Personally, I think it is tamer than it looks. the track is elevated, but the dips/speed are pretty mild.
Rat is a lot like Minnie/Mickey Railway, but slightly tamer and WAY better. Both are pretty tame, but Railway is a little bit hurky-jerky.Rat is pretty smooth all the way through.
In part, she will only know for sure when she decides to try each one. Every person reacts differently. I have read on these boards of people who are fine with every ride except the Small World Dolls scare them.
Last, if she does enjoy or even tolerates any ride she was iffy about, often the VERY BEST thing is to re-ride it as soon as possible. We are all a little afraid the first time we ride a new attraction.