Awww, you're not a bad mom!

to you! In fact you are a great mom because you are noticing a change in your little princess's behavior and you are concerned... to me that means you really know your little sweetie and that's awesome!

Some people just stop there; they notice the difference, but they just shrug and don't worry about it, but you want to help which is great!
Reading the age of your little one (7 months), and then following up with how she is crying unless she has something to put in her mouth (even if it's not nursing - sounds like she just wants anything in there, because if she was hungry, then a finger or a blanket etc wouldn't be enough).... all of those things together sound like someone who is the perfect age for teething, and is trying to get some relief with anything in her mouth, and the comfort of the presence of her mommy. If this is the case, right now is a good time to slow down a bit with your No Cry Sleep Solution "Sleep Plan" while she gets over this most recent bout of needing your comfort during this painful time. This happened to our DS as well, and he was such a good sleeper until 7 months when he just was so wakeful and suddenly needed a pacifier even though he never had one before... It helped (like the thumb helped your DS you said), but it's a mixed blessing because now our DS is almost 3 and a half, and he still wants that pacifier sometimes at night... most of the night he doesn't need it, but it's just that he thinks he does before he falls asleep! Oh well! I've never seen a 16 year old who needs one at night so I guess these things eventually work themselves out.
Does this sound like it could be a possibility? If not, let's continue to brainstorm to come up with other ideas!