Hi,
if I'm not mistaken you meant that 'Z' icon filling up during the night fun. If it goes up too fast it's best you can:
- buy dexterity upgrades which lower the rate at which it fills up,
- pat her head during some interactions which will lower the rate a little as well,
- raise relationship level so she accepts other gifts like lip balm, lotion and green tea
- use sleeping salts and focus pills which will help with her wakefulness and make minigames easier
As for her suspicion (if you end night with her undressed and don't wipe cum) she will be "mad" and won't accept gifts like green tea, lip balm and lotion from you, if this is the case you have to wait few days so she won't be suspicious anymore.
Hope this helps,
Cheers