The first time Jane realises that she has feelings for her best friend is when the couch gets delivered to her now burnt-out apartment. The cute look on her face when the delivery men turn up and announce that they have a sofa for Rizzoli is something that sticks with her. But she doesn't do anything about it for a variety of reasons, the first one being it was a highly emotional time and she really doesn't want to make any decisions when her mind is all over the place.
The second reason is, she doesn't want to lose Maura. She's her best friend and the thought of losing her was almost too much for her right now, and she'd rather keep her as a friend than risk anything more.
For now, she's just happy to be around Maura, maybe one day something will come of it, but for now, she was mostly happy to try and make it work with someone else, although that small voice in the back of her head that kept talking about Maura just wouldn't let that happen.