Kids will get through eventually, but parents feel much worse.

Several things I learnt from our preschool:
1. Talk to Ruru about routines in daycare. Tell her the programs of the day in the order of happening (like playing, snacks, outside time, lunch, nap, then parents coming) so that she knows what to expect. Also tell her things that she is expected to do by herself: eating? drinking from what type of glass/bottle? her own blanket and lovy, how they change diapers etc etc.
2. If you decide to stay, tell her and stay the whole time. This step helps to reassure Ruru that this is a safe environment, and her teacher is someone you trust. No nasty surprise for her.
3. If you leave, do NOT come back until pickup time. Of course you can peek from outside, but don't let her see you. Coming back and leave repeated just confuses her.
4. Set up a routine for morning good-bye: like read one book or play one game, then kiss and leave. Keep it to less than 10 min. The longer, the harder.
5. Be prepared mentally for separation period. It usually takes 8 weeks at least. Some kids 1 week, others 8 months.
6. It is normal for her to cry. She needs to cry and fall apart before she can establish bonding with the teachers. You stay out of this. But crying is only the first step. Later she may throw tandrums, night wakening and crying etc, lots of behaviour things. Be prepared. It is all normal.
Kids grow up through this process. They will do fine. Good luck.