I never really did much tummy time with DD either. She learned to roll fairly quickly and was able to hold her head up quickly too so I don't think a lack of tummy time did much to disadvantage her! I'd probably be more worried about flat spots than not reaching physical developmental milestones, so if her head is looking fine I wouldn't stress too much.

Can you carry her over your arms so she is facing down? Another mum I know used to lay their bub on a footstool in front of the tv (not ideal I know, but it kept her entertained for a few minutes and she kind of forgot she was on her tummy). Or you could probably just carry her around in a semi-upright position (change to an upright position once she can hold her head up properly) just so she isn't lying on her back all the time.

will she lie on her side at all? Maybe try that and just pop her on her tummy for a few seconds then roll her back to get her used to it.