Perfectly normal behaviour for a 4 month old!!
There is a huge growth spurt at 4 months, some feed more frequently, some sleep more, some do both. The best thing to do is to feed her when she is hungry day or night. Most babies don't drop night feeds until solids are established, so around 7/8 months. Some do drop the night feeds earlier though so you never know.
Should I introduce solids at this point?
No, it's milk she needs not solids as milk has more fats and calories per oz than the early solids and that's what fills her up not things like rice cereal which are pretty empty calories. Milk needs to be her main source of calories and nutrients until she is 1, the solids come in slowly from about 6 months to gradually replace milk.
HTH!
Laura