If your girlfriend get alert every time whenever you touch her mobile or if she neglects you while texting, You should take notice because there is something that she is hiding from you. She must be talking secretly o chatting secretly in your presence and feels uncomfortable in your company.
If she suddenly gets in the mood to change her looks, makes her styles more prominent then it might be because she wants to impress someone else.
If she has started giving lame excuses about being caught up in the work or being blocked in the traffic then she must have been spending time with someone else and ignoring you indirectly. For example, if she started ignoring the daily time spent with you, like going for a walk or watching serials, with all those excuses.