Another new tooth for Lucy

Yesterday, Lucy cut a new tooth while we were at the grocery store. That makes five now.

She had been cranky for a few days, and had been eating and sleeping more than usual. In my great maternal wisdom, I had credited her recent attempts to sit from crawling with the deficit in her energy levels. For many days now, she has been fully extending her back legs from a crawling position. Her feet are flat on the floor and her arms remain on the floor (so it's sort of a downward-facing dog on forearms). Unfortunately, she has not mastered the backing-up into a seated position part yet - so there have been many horrific face plants lately. It doesn't help that we have no carpeted surfaces. I try to keep her on the rug in the living room, but these days she goes whereever she wants. I have to keep her Robeez on all the time now, to ensure that she has enough traction for these manoeuvers.
At any rate... I took her out with me to fetch a few items from the grocery store, giving Greg and Becca a chance to enjoy the snow. Lucy was madly chomping on her vibro-teether. Suddenly, I saw blood on her lips. She opened her mouth, and I saw blood on her tongue. I'll admit to a moment of panic. My first thought was to check the tooth I knew she was labouring on. Nothing. That's when my heart truly began to pound. Could she have gotten something inappropriate into her mouth when I was looking elsewhere? Could she have bitten herself? I finally managed to convince her to keep her mouth open long enough for me to run a finger around. That's when I discovered that she had cut a completely different tooth than expected. This new tooth is on the same side as the one I was anticipating, but on the top instead of the bottom. When I found it, it had just pierced the gum and there was still blood around the edges.
I am beginning to notice that Lucy is expressing frustration when her explorations are curtailed. She is an incredibly curious baby, and like most babies her age, she is very interested in completely inappropriate objects (and locales). She would like nothing better than to get into Rebecca's room. Sometimes she does (because she's fast, and we're busy). Sometimes we shut the door. This annoys her to no end. She also expresses frustration via various wails and cries, when I take an object off the floor that she had clearly been heading towards. Her second favourite place to attempt to enter is the vestibule. Lucy is obsessed with shoes. She wants to go after any and all shoes, and puts them in her mouth. This is a challenge lately because (as I said above), she is almost perpetually in her Robeez. Sometimes she decides to gnaw on them in the middle of a meal - even when her face is covered in sweet potato purée. Sometimes she decides that one of the other Moms at Fitmom has more attractive sneakers than I do, and she attacks them. The worst scenario - as you may have already imagined - is when Rebecca's shoes are accessible to Lucy.
At this time, neither Lucy nor Rebecca seem to be experiencing the upsides of having a sibling. Rebecca screams whenever Lucy starts crawling towards her or some object (any object really) with ear-shattering exclamations like "HELP! Lucy crawlin'!!!". Rebecca is also inclined to try to change Lucy's direction by means of physical intervention. Lucy, who is obsessed with Rebecca, is heartbroken when Rebecca shuts her bedroom door in her face. Also, both girls seem to be more insistent about having my attention lately - but in order for me to spend time with them that does not involve trauma for either party - I have to separate them! This makes life a lot more complicated. It is very hard to achieve this. Obviously - Lucy's nap times help, and I have staggered their bedtimes a bit (they were previously synchronous), but it is difficult!