If you can find an "old-fashioned" playpen (the SQUARE ones with the hard bottom, not the "little bitty rectangles" they sell now), you can put your tree in that. Works great for cats and rambunctious puppies, too! The playpen is also great for keeping the presents out of reach! (I was also looking for an alternative solution, so I wouldn't have to say "no touch" every time I turned around. That gets to be "no fun" for ME!!)
I haven't got any advice about the tree, because I haven't had a "live" tree in something like 30 years....MAJOR allergy to cedar/pine!! We bought a great little tree (to fit our apt) last year that has fiber optic lights on it, and our little boy loved it!!
As for the decorations, you might want to consider putting the "kid safe" ornaments on the whole tree, and not just the bottom. This is because if she does just "bump" the tree just right, one of those glass ornaments can fall and shatter *everywhere*. This would be a great year to do a "Disney-theme" tree, if you're into "themes".
Hope y'all have a MERRY CHRISTMAS!