I just wanted to underline an aspect of Mandy Thompson's ability that can easily be overlooked:
What Mandy's ability does is that, once per round, when an investigator at her location searches their deck (or the encounter deck), they can either search for 1 additional card or search 3 cards deeper. The obvious thing here is that Mandy can support other investigators with her ability using her cards for them, but what can easily be missed is that other investigators can activate Mandy's ability using THEIR OWN cards. That can create some interesting interactions between some cards and Mandy's ability and certain cards can become more powerful. This can lead to the creation of some strong builds that work around Mandy's ability and specific cards, which is really interesting.
I'd like to go through a list of cards that when used by other investigators they (usually) become better if Mandy Thompson's ability gets in the mix:
Anna Kaslow: While Anna Kaslow is really bad for Mandy, as putting her into play at the beginning of the game makes it guarranteed that she will hit her weakness, it's rather beneficial for other investigators to have her in their deck, as with Mandy's ability it's pretty much guarranteed that they will hit 2 tarot cards with her. That's pretty strong.
Prepared for the Worst: This card becomes a lot more reliable when combined with Mandy's ability. Going 12 cards deep increases your chances to find a weapon substantially and it can be huge to certain builds, specifically ones that are built around certain weapons (Becky and Flamethrower comes to mind). The option to get 2 weapons is also nice.
Arcane Initiate: Searching 6 cards for a spell makes it far more likely to hit a spell and on spell-heavy decks the option to dig for 2 spells can also be good.
Backpack: This card is perfectly usable by Mandy as well, but the ability for another investigator to go 9 cards deep with it can be huge, making it far more consistent and increasing substantially the chances to get a specific item that they 've built around (like Crystallizer of Dreams or The Skeleton Key).
Calling in Favors: While the interaction between Mandy's ability and this card is very powerful, Mandy herself doesn't quite have the suitable array of allies to put it into good use (I don't mean it's bad, it's just not great). Another investigator however can make great use of this. Putting into play 2 allies from your deck at reduced cost can be huge in certain cases. Just imagine someone like Tommy Muldoon or Leo Anderson using Calling in Favors on something like Brother Xavier and putting into play an Agency Backup and a second Brother Xavier at the cost of 1 action and 3 resources! That's outright broken!
Flare: That's one of the most powerful interactions. Still usable by Mandy, but another investigator can use it as well. Put 2 allies into play from your deck. Enough said.
Rabbit's Foot (3): Becomes a lot better with Mandy's ability. Looking for a specific card? Go 3 cards deeper. Are you already digging deep? Get an additional card. Nice thing.
On the Hunt: Searching for 2 enemies with On the Hunt isn't really the thing you want to be doing unless you 're using Flamethrower, but the ability to go 12 cards deep allows you to dig for specific enemies. This can be useful if you 're looking for VP enemies or if you want certain enemies to get out of the way. Either way, it's an interesting interaction. Not powerful, just interesting.
Smuggled Goods: This was already good, but with Mandy's ability it becomes way better. Searching for 2 illicit cards makes this really nice for Finn Edwards. How about digging out from your deck those Lockpicks and Pickpocketing on turn 1 and still get to use this again later at some point during the scenario, possibly at the same power level? Simply awsome.
Stick to the Plan: This one is a little weird, but if it works it's actually really great. At every scenario, every investigator starts at the same location, so the one using Stick to the Plan can activate Mandy's ability when searching their deck and stick a 4th event under the permanent. If this actually works it's really nice! Understanding whether this works or not probably requires a thorough aknowledgement of the rules (which I don't really have) and/or some clarification from FFG. The reasonable question posed here is whether investigator abilities are active during setup. This question gets a little complicated if you take into account that most investigator abilities have a once-per-round designator. During setup the round hasn't even begun yet, so there could be an argument made that since the round hasn't begun yet they are not active. On the other hand, if investigator abilities are always active, this may mean that they are also active during setup. A rules expert might be able to put some light into this. Anyway, the thing is that, if this actually works, it's really awsome!
Concluding, I 'd like to state that there are cards that get benefit from Mandy's ability that miss they eye and some cards, as you can see, become a lot stronger with her, and when you have Mandy Thompson in your team you can create some builds that would otherwise be suboptimal or less good. Taking into account this stuff, I think Mandy Thompson has great potential and it's always nice to have her as a teammate. I personally love Mandy, as I believe that her ability is very strong. She's my favourite so far.