Perhaps she has discovered that saying "I love you" after every interaction makes those words lose its sparkle... It becomes more like part of the greeting than an actual expression of love.

Like how people say "hey how are you?" / "Fine"..... Automatic replies during greeting, no real substance.

My bf and I don't say it to each other all the time anymore either, but as long as we are showing love in our actions, love is a verb as they say after all, then I have no complaints and neither does he.

Its like how my ex used to say "I'm sorry"... The words lost their meaning to me. I prefer someone show me remorse amd keep their apologies to themselves, because those words have become hollow and lack any real depth.

By all means talk to her if you must, in person, but I personally doubt you have anything to worry about if this is your only concern.