Dunjin said:
I spoke to her yesterday about it, and she explained to me that she has a short attention span and tends to zone out when she's not directly involved...
She explained that she's having trouble envisioning scenes...
I really want to find a way to bring her in. How do I do it?
1) Involve her. Directly! Have NPCs speak directly to her. Ask her, specifically, what does she want to do. Instead of saying "The man tells you he's taking his cow to the barn," say "The man tells you 'My name is Hiram, and this is Bossy, my prize Milch-cow. We're going to the barn for a good milking, aren't we, girl?' The Man then pats old Bossy, who moos, contentedly."
2) If she's having trouble envisioning things, then you need to be more descriptive... Next time they do a dungeon crawl, start by getting up and turning off the lights. Then narrate.
You enter the doorway, leaving the light of the sun behind. The room you enter is full of palpable darkness... There is no sound here, except for what you make, yourselves. The air is dank, and stale, with a musty smell that permeates everything. You can see nothing past where the light of the sun enters through the doorway, behind you. The dark stone of the floor seems to soak up the light. A chill breeze blows past you, out the door you just entered, as though it wishes to escape this place...
After reading them something like that, ask each of them to roll Initiative, and then ask them - in order of Initiative, "What do you want to do?" Once someone lights a torch or lantern, turn the lights back on, and return to your seat, narrating the rest of the adventure, likewise. That usually gets the attention of everyone, even if they hate set-dressing.
3) Bring her in at her own speed. If she's having trouble envisioning things, use better descriptions, maps, and illustrations of the creatures met... To many people, "Kobold" conjures up an image of Telly Savalis, if anything at all...
If she's having troubles envisioning what to do, then you're just going to have to be patient with her, until she figures out what her PC wants to try. Once she does, if it isn't adventure-wrecking, it's best if you just let "her idea" succeed. That will probably produce more interest, and more ideas.
If she's not into all the aspects of RPing, but more a Hack'n'slasher, then maybe combat is just easier for her to understand... It has a clear-cut beginning, ending, and generally simple rules... You could try running something else that she can do in a similar fashion. If she just wants more combat, work in more combats with larger numbers of lower-level opponents, instead of fewer higher-CR critters, and let her enjoy combat.