Secretly, stealthily, and clandestinely are words. Those mean surreptitiously.
secretly, stealthily,
See mean-8. Or get a dictionary.
peep
That is not a word in the English language.
There are a couple words which can be used to mean follow secretly. Those words include shadow and the word stalk.
A chuzada is when they secretly tap your phone without your consent
Secretly is an adverb.
The word for looking at someone or something secretly is "spying" or "peeking".
The word you are looking for is "conspire". It means to plan something secretly with others.
infatuated?
Covertly
The word eavesdrop means to secretly listen in on a private conversation. The word come from Middle English. In some situations, eavesdropping is considered to be illegal.
If by secretly you meant cautiously then walking stealthily or tip toeing .
No secretly s an adverb, secret can be an adjective eg She has a secret friend
Peep.
secretly