Unfortunately, if she denies being at fault, there's nothing you can do if there is no video evidence.
The colour being the same will be considered coincidental - it could have happened on another day/weekend, by a same coloured car etc.

You basically have 2 options - either politely bring it up with her and ask whether she may have inadvetantly bumped your car (you cant flat out accuse her or you're the one who could end up in trouble with HR if it gets out of hand) or you go to HR first, repeat to them what youve posted here ask them for their opinion. Its likely they will say exactly what I've said. Remember also she may genuinely have been oblivious to any contact made due to a variety of reasons.

One thing you can do that might help is to go out to her car during the day randomly and check to see if her driver's door has any of your paint on the rim/edge where it would have hit your door. Sometimes there is a two way transfer of colour. If there is take a snap. Again I think it will get passed of as coincidental but it could help.