Because of the unwieldy dialogue system which requires voiced player dialogue I've added a series of bonuses and features the player may only find by accident since there are no convos with Heather to let you know these things even exist:

Here's what's available (bonuses based on perks can only be rewarded after Heather has been with the player for one level). Most of them you have to talk to Heather to finish up the bonus reward (she'll give you a greeting specific to the bonus and give the appropriate reward).

Player Choosen Perks produce improvements in Heather's abilities:
1.  If you take the second rank of Strong Back
-Heather gains +25 carryweight
2.  If you take the fifth rank of Sneak
-Heather becomes (mostly) invisible when you sneak. I lessened the effect so you can kinda see where she is rather than Heather being truly, completely invisible.
3.  If you take the fourth ranks of Armorer or Toughness or the third rank of Admantium Skeleton
-Heather's Damage Resistance increased +30
-Heather's Energy Resistance + 30

Other
4. If you give Heather 10 Noodle Cups (trade them into her inventory until she has 10)
-Heather's Health increases +25
5. If you give Heather your spouse's wedding ring and equip it on her and you have maxed affinity romantically (she'll recognize that you've equipped it on her at any affinity level but the bonus won't happen until affinity has been maxed)
-She gives player a special token of her affection
-"Married!" perk awarded to both player and Heather. The player and Heather both gain +25 Carryweight and deal 10% more damage when the player travels exclusively with Heather (won't count against having Dogmeat)
6.  If you equip a set of Children of Atom rags 
-Heather gives the player a very damaged Hazmat Suit
7. If you use 20 of Heather's Alternative Medicine products
- "The Power of Alternative Medicine" perk is awarded
- you gain +10 Radiation Resistance
- your health now regenerates slowly
- your limb damage is reduced by 10%
8. if you take her to Weston Water Treatment Plant she will make a new edition of the Wasteland Survival Guide and put it into the mailbox in the bunker (this happens 10 levels after you've gone there).
-On reading the magazine you'll be awarded the "Swimming with Super Mutants" perk. Player takes 5% less damage from Super Mutants.
9. If you are at Power Noodles with Heather and you tell her to sit in one of the stools she will do so and order noodles from Takahashi. This won't work at every chair. Companions AI, including Heather's is terrible in this game because of navmesh problems.